diff --git a/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/CustomAction.dll b/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/CustomAction.dll
index 1ccf4c10..c0ad6483 100644
Binary files a/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/CustomAction.dll and b/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/CustomAction.dll differ
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/DispalyMessage.dll b/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/DispalyMessage.dll
index 8b0b12cd..64f9c068 100644
Binary files a/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/DispalyMessage.dll and b/Source/src/WixSharp.Samples/Wix# Samples/DTF (ManagedCA)/Different Scenarios/ExternalAssembly/DispalyMessage.dll differ
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/Extensions/setup.cs b/Source/src/WixSharp.Samples/Wix# Samples/Extensions/setup.cs
index f2b2a3df..12c5e489 100644
--- a/Source/src/WixSharp.Samples/Wix# Samples/Extensions/setup.cs	
+++ b/Source/src/WixSharp.Samples/Wix# Samples/Extensions/setup.cs	
@@ -36,6 +36,7 @@
 /// </code>
 ///
 /// </summary>
+
 class Script
 {
     static public void Main()
@@ -144,7 +145,7 @@ public void PseudoProcessWithNewComponentAndFeature(ProcessingContext context)
                .Add(element);
 
         context.XParent
-               .Parent(Compiler.ProductElementName)
+               .Parent("Product")
                .AddElement("Feature", "Id=TestFeature;Title=Test Feature;Absent=allow;Level=1")
                .AddElement("ComponentRef", "Id=TestComponent");
     }
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/External_UI/Msi/MyProduct.msi b/Source/src/WixSharp.Samples/Wix# Samples/External_UI/Msi/MyProduct.msi
index a27d7b94..91eda471 100644
Binary files a/Source/src/WixSharp.Samples/Wix# Samples/External_UI/Msi/MyProduct.msi and b/Source/src/WixSharp.Samples/Wix# Samples/External_UI/Msi/MyProduct.msi differ
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/IIS/XMLInjection/setup.cs b/Source/src/WixSharp.Samples/Wix# Samples/IIS/XMLInjection/setup.cs
index b262e171..395893a3 100644
--- a/Source/src/WixSharp.Samples/Wix# Samples/IIS/XMLInjection/setup.cs	
+++ b/Source/src/WixSharp.Samples/Wix# Samples/IIS/XMLInjection/setup.cs	
@@ -2,9 +2,9 @@
 //css_ref ..\..\..\Wix_bin\SDK\Microsoft.Deployment.WindowsInstaller.dll;
 //css_ref System.Core.dll;
 using System;
-using System.Linq;
 using System.Xml;
 using System.Xml.Linq;
+using System.Linq;
 using WixSharp;
 using WixSharp.CommonTasks;
 
@@ -13,13 +13,13 @@ class Script
     static public void Main()
     {
         var project =
-                new Project("My Product",
-                    new Dir(@"%ProgramFiles%\MyCompany",
-                        new Dir(@"MyWebApp",
-                            new File(@"MyWebApp\Default.aspx"),
-                            new File(@"MyWebApp\Default.aspx.cs"),
-                            new File(@"MyWebApp\Default.aspx.designer.cs"),
-                            new File(@"MyWebApp\Web.config"))));
+               new Project("My Product",
+                   new Dir(@"%ProgramFiles%\MyCompany",
+                       new Dir(@"MyWebApp",
+                           new File(@"MyWebApp\Default.aspx"),
+                           new File(@"MyWebApp\Default.aspx.cs"),
+                           new File(@"MyWebApp\Default.aspx.designer.cs"),
+                           new File(@"MyWebApp\Web.config"))));
 
         project.GUID = new Guid("6fe30b47-2577-43ad-9095-1861ba25889b");
 
@@ -36,8 +36,8 @@ static void Compiler_WixSourceGenerated(System.Xml.Linq.XDocument document)
         XElement aspxFileComponent = (from e in document.FindAll("File")
                                       where e.Attribute("Source").Value.EndsWith("Default.aspx")
                                       select e)
-                                      .First()
-                                      .Parent;
+                                     .First()
+                                     .Parent;
 
         string dirID = aspxFileComponent.Parent.Attribute("Id").Value;
 
@@ -52,13 +52,13 @@ where e.Attribute("Source").Value.EndsWith("Default.aspx")
                                       new XAttribute("Id", "TestWebApplication"),
                                       new XAttribute("Name", "Test"))));
 
-        document.Root.Select(Compiler.ProductElementName)
+        document.Root.Select("Product")
                      .Add(new XElement(ns + "WebSite",
                               new XAttribute("Id", "DefaultWebSite"),
                               new XAttribute("Description", "Default Web Site"),
                               new XAttribute("Directory", dirID),
                               new XElement(ns + "WebAddress",
-                                  new XAttribute("Id", "AllUnassigned"),
-                                      new XAttribute("Port", "80"))));
+                                   new XAttribute("Id", "AllUnassigned"),
+                                    new XAttribute("Port", "80"))));
     }
 }
\ No newline at end of file
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/InjectXML/setup.cs b/Source/src/WixSharp.Samples/Wix# Samples/InjectXML/setup.cs
index 2597a401..5de7190c 100644
--- a/Source/src/WixSharp.Samples/Wix# Samples/InjectXML/setup.cs	
+++ b/Source/src/WixSharp.Samples/Wix# Samples/InjectXML/setup.cs	
@@ -77,7 +77,7 @@ static public void Main()
 
     private static void InjectImages(System.Xml.Linq.XDocument document)
     {
-        var productElement = document.Root.Select(Compiler.ProductElementName);
+        var productElement = document.Root.Select("Product");
 
         productElement.Add(new XElement("WixVariable",
                                new XAttribute("Id", "WixUIBannerBmp"),
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/Install Files/setup.cs b/Source/src/WixSharp.Samples/Wix# Samples/Install Files/setup.cs
index 13b5b9fa..648a0a8e 100644
--- a/Source/src/WixSharp.Samples/Wix# Samples/Install Files/setup.cs	
+++ b/Source/src/WixSharp.Samples/Wix# Samples/Install Files/setup.cs	
@@ -15,9 +15,6 @@ class Script
 {
     static public void Main()
     {
-        Compiler.WixLocation = @"C:\Users\oleg.shilo\.dotnet\tools\.store\wix\4.0.0\wix\4.0.0\tools\net6.0\any";
-        Compiler.IsWix4 = true;
-
         File f;
         var project =
             new Project("MyProduct",
@@ -43,8 +40,6 @@ static public void Main()
 
         project.GUID = new Guid("6f330b47-2577-43ad-9095-1861ba25889b");
 
-        project.UI = WUI.WixUI_InstallDir;
-
         project.EmitConsistentPackageId = true;
         project.PreserveTempFiles = true;
         project.PreserveDbgFiles = true;
@@ -58,7 +53,7 @@ static public void Main()
 
         project.WixSourceGenerated += Compiler_WixSourceGenerated;
 
-        project.BuildMsiCmd();
+        project.BuildMsi();
     }
 
     private static void Compiler_WixSourceGenerated(XDocument document)
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/Managed Setup/Self-executable_Msi/ManagedSetup.msi b/Source/src/WixSharp.Samples/Wix# Samples/Managed Setup/Self-executable_Msi/ManagedSetup.msi
deleted file mode 100644
index e6e56ba7..00000000
Binary files a/Source/src/WixSharp.Samples/Wix# Samples/Managed Setup/Self-executable_Msi/ManagedSetup.msi and /dev/null differ
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/MultipleInstances Install/setup.cs b/Source/src/WixSharp.Samples/Wix# Samples/MultipleInstances Install/setup.cs
index 243ecbb1..32dfb1fb 100644
--- a/Source/src/WixSharp.Samples/Wix# Samples/MultipleInstances Install/setup.cs	
+++ b/Source/src/WixSharp.Samples/Wix# Samples/MultipleInstances Install/setup.cs	
@@ -4,12 +4,12 @@
 
 using System;
 using System.IO;
-using System.Linq;
 using System.Xml;
 using System.Xml.Linq;
-using Microsoft.Deployment.WindowsInstaller;
+using System.Linq;
 using WixSharp;
 using File = WixSharp.File;
+using Microsoft.Deployment.WindowsInstaller;
 
 public class Script
 {
@@ -44,7 +44,7 @@ static public void Main()
                             new XAttribute("ProductCode", Guid.NewGuid()),
                             new XAttribute("ProductName", "My Product " + instance)));
 
-                document.Root.Select(Compiler.ProductElementName).Add(instanceTransforms);
+                document.Root.Select("Product").Add(instanceTransforms);
             };
 
         Compiler.BuildMsi(project);
diff --git a/Source/src/WixSharp.Samples/Wix# Samples/Skip_UIDialog/setup.cs b/Source/src/WixSharp.Samples/Wix# Samples/Skip_UIDialog/setup.cs
index 5fa16f7d..0609a1d8 100644
--- a/Source/src/WixSharp.Samples/Wix# Samples/Skip_UIDialog/setup.cs	
+++ b/Source/src/WixSharp.Samples/Wix# Samples/Skip_UIDialog/setup.cs	
@@ -33,9 +33,9 @@ static public void Main()
 
     static void Compiler_WixSourceGenerated(XDocument document)
     {
-        document.Root.Select(Compiler.ProductElementName)
+        document.Root.Select("Product")
                      .Add(XElement.Parse(
-                          @"<UI>
+                            @"<UI>
                                   <Publish Dialog=""WelcomeDlg"" Control=""Next"" Event=""NewDialog"" Order=""5"" Value=""InstallDirDlg"">1</Publish>
                                   <Publish Dialog=""InstallDirDlg"" Control=""Back"" Event=""NewDialog"" Order=""5""  Value=""WelcomeDlg"">1</Publish>
                               </UI>"));
diff --git a/Source/src/WixSharp.Test/IssueFixesTest.cs b/Source/src/WixSharp.Test/IssueFixesTest.cs
index 572b16b6..4281bd17 100644
--- a/Source/src/WixSharp.Test/IssueFixesTest.cs
+++ b/Source/src/WixSharp.Test/IssueFixesTest.cs
@@ -434,9 +434,9 @@ public void Should_Handle_EmptyFeatures()
 
             var doc = XDocument.Load(wsxfile);
 
-            var product = doc.FindSingle(Compiler.ProductElementName);
+            var product = doc.FindSingle("Product");
 
-            var rootFeature = doc.Select($"Wix/{Compiler.ProductElementName}/Feature");
+            var rootFeature = doc.Select("Wix/Product/Feature");
             Assert.NotNull(rootFeature);
 
             var docsFeature = rootFeature.Elements()
diff --git a/Source/src/WixSharp/Action.cs b/Source/src/WixSharp/Action.cs
index 6d293fad..d24069f6 100644
--- a/Source/src/WixSharp/Action.cs
+++ b/Source/src/WixSharp/Action.cs
@@ -27,8 +27,6 @@ THE SOFTWARE.
 
 #endregion Licence...
 
-using System.Xml.Linq;
-
 namespace WixSharp
 {
     /// <summary>
@@ -176,12 +174,6 @@ public Action(Id id, Return returnType, When when, Step step, Condition conditio
         /// </summary>
         public Condition Condition = Condition.NOT_Installed;
 
-#if WIX3
-        internal object ToXmlCondition() => this.Condition.ToXValue();
-#else
-        internal XAttribute ToXmlCondition() => new XAttribute("Condition", this.Condition.ToString());
-#endif
-
         /// <summary>
         /// The sequence number for this action. Mutually exclusive with Before, After, and OnExit of <see cref="When"/> field.
         /// </summary>
diff --git a/Source/src/WixSharp/AutoElements.cs b/Source/src/WixSharp/AutoElements.cs
index 52e4c068..ad94f3dc 100644
--- a/Source/src/WixSharp/AutoElements.cs
+++ b/Source/src/WixSharp/AutoElements.cs
@@ -415,7 +415,7 @@ select s.Attribute("Icon").Value).Distinct())
                 shortcut.Attribute("Icon").Value = iconId;
             }
 
-            XElement product = doc.Root.Select(Compiler.ProductElementName);
+            XElement product = doc.Root.Select("Product");
 
             foreach (string file in icons.Keys)
                 product.AddElement(
@@ -426,7 +426,7 @@ select s.Attribute("Icon").Value).Distinct())
 
         static void InjectPlatformAttributes(XDocument doc)
         {
-            var is64BitPlatform = doc.Root.Select(Compiler.IsWix4 ? "Package" : "Product/Package").HasAttribute("Platform", val => val == "x64");
+            var is64BitPlatform = doc.Root.Select("Product/Package").HasAttribute("Platform", val => val == "x64");
 
             if (is64BitPlatform)
             {
@@ -599,7 +599,7 @@ static void InsertEmptyComponentsInParentDirectories(XDocument doc, XElement ite
 
         static void CreateEmptyComponentsInDirectoriesToRemove(XDocument doc)
         {
-            XElement product = doc.Root.Select(Compiler.ProductElementName);
+            XElement product = doc.Root.Select("Product");
 
             // Create new empty components in parent directories of components with no files or registry
             var dirsWithNoFilesOrRegistryComponents = product.Descendants("Directory")
@@ -615,7 +615,7 @@ static void CreateEmptyComponentsInDirectoriesToRemove(XDocument doc)
 
         internal static void HandleEmptyDirectories(XDocument doc)
         {
-            XElement product = doc.Root.Select(Compiler.ProductElementName);
+            XElement product = doc.Root.Select("Product");
 
             var dummyDirs = product.Descendants("Directory")
                                    .SelectMany(x => x.Elements("Component"))
@@ -683,7 +683,7 @@ internal static void InjectAutoElementsHandler(XDocument doc, Project project)
             InjectShortcutIcons(doc);
             HandleEmptyDirectories(doc);
 
-            XElement product = doc.Root.Select(Compiler.ProductElementName);
+            XElement product = doc.Root.Select("Product");
 
             int? absPathCount = null;
             foreach (XElement dir in product.Element("Directory").Elements("Directory"))
diff --git a/Source/src/WixSharp/Bootstrapper/BootstrapperApplication.cs b/Source/src/WixSharp/Bootstrapper/BootstrapperApplication.cs
index bd617e85..d010efb3 100644
--- a/Source/src/WixSharp/Bootstrapper/BootstrapperApplication.cs
+++ b/Source/src/WixSharp/Bootstrapper/BootstrapperApplication.cs
@@ -3,11 +3,7 @@
 using System.IO;
 using System.Linq;
 using System.Xml.Linq;
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 
 using sys = System.IO;
 
diff --git a/Source/src/WixSharp/ComRegistration.cs b/Source/src/WixSharp/ComRegistration.cs
index fa3de6bf..0f55f236 100644
--- a/Source/src/WixSharp/ComRegistration.cs
+++ b/Source/src/WixSharp/ComRegistration.cs
@@ -114,7 +114,7 @@ public AppId()
         /// <exception cref="ValidationException"></exception>
         public void Process(ProcessingContext context)
         {
-            string[] AdvertiseParents = { "Fragment", "Module", Compiler.ProductElementName };
+            string[] AdvertiseParents = { "Fragment", "Module", "Product" };
 
             // If the parent element is a Fragment, Module, or Product, ensure Advertised is true.
             if (!Advertise && AdvertiseParents.Any(s => s == context.XParent.Name.LocalName))
diff --git a/Source/src/WixSharp/CommonTasks.cs b/Source/src/WixSharp/CommonTasks.cs
index e8c7cd9a..d1762aa3 100644
--- a/Source/src/WixSharp/CommonTasks.cs
+++ b/Source/src/WixSharp/CommonTasks.cs
@@ -32,14 +32,10 @@ THE SOFTWARE.
 using System.Windows.Forms;
 using System.Xml.Linq;
 using System.Xml.XPath;
+using Microsoft.Deployment.WindowsInstaller;
 using WixSharp;
 using WixSharp.Bootstrapper;
 using WixSharp.Controls;
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 using IO = System.IO;
 
 namespace WixSharp.CommonTasks
@@ -772,7 +768,7 @@ static public File AddAssociations(this File file, params FileAssociation[] item
 
         //         progId.SetAttribute("Icon", iconId);
 
-        //         doc.FindSingle(Compiler.ProductElementName)
+        //         doc.FindSingle("Product")
         //                 .AddElement("Icon", $@"Id={iconId};SourceFile={iconPath}");
         //     };
         // }
@@ -1059,7 +1055,7 @@ static public Project SetVersionFrom(this Project project, string fileId, bool s
         {
             project.SetVersionFromIdValue = fileId;
             project.WixSourceGenerated += document =>
-                document.FindSingle(Compiler.ProductElementName)
+                document.FindSingle("Product")
                         .AddAttributes("Version=!(bind.FileVersion." + fileId + ")");
 
             if (setProjectVersionAsWell)
diff --git a/Source/src/WixSharp/Compiler.Bootstrapper.cs b/Source/src/WixSharp/Compiler.Bootstrapper.cs
index 7ff31edc..6eec53eb 100644
--- a/Source/src/WixSharp/Compiler.Bootstrapper.cs
+++ b/Source/src/WixSharp/Compiler.Bootstrapper.cs
@@ -37,12 +37,8 @@ THE SOFTWARE.
 using System.Text.RegularExpressions;
 using System.Windows.Forms;
 using System.Xml.Linq;
-using WixSharp.Bootstrapper;
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
+using WixSharp.Bootstrapper;
 using IO = System.IO;
 
 namespace WixSharp
diff --git a/Source/src/WixSharp/Compiler.cs b/Source/src/WixSharp/Compiler.cs
index 6d46cd80..6ed4120d 100644
--- a/Source/src/WixSharp/Compiler.cs
+++ b/Source/src/WixSharp/Compiler.cs
@@ -27,37 +27,19 @@ THE SOFTWARE.
 
 #endregion Licence...
 
+using Microsoft.Deployment.WindowsInstaller;
 using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using System.Runtime.CompilerServices;
 using System.Text;
 using System.Text.RegularExpressions;
 using System.Threading;
 using System.Xml.Linq;
 using WixSharp.CommonTasks;
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 using IO = System.IO;
 
-/*
- Wix4 challenges
-
-- No samples
-- No API porting documentation (only for v3 vs v4 CLI). It's not clear how to port no longer existing attributes (e.g. Package.Languages) 
-- How v3 WiX extensions are mapped to the nuget packages for v4 
- 
- 
- 
- 
- */
-
-
 namespace WixSharp
 {
 
@@ -307,11 +289,6 @@ public partial class Compiler
         /// </summary>
         static public string CandleOptions = "-sw1026 ";
 
-        /// <summary>
-        /// WiX compiler <c>wix.exe</c> options (e.g. "-define DEBUG"). Available only in WiX v4.*
-        /// </summary>
-        public static string WixOptions = "";
-
         static string autogeneratedWxsForVS = null;
 
         static Compiler()
@@ -594,39 +571,13 @@ static void BuildCmd(Project project, string path, OutputType type)
 
             string wixLocationEnvVar = $"set WixLocation={WixLocation}";
             string compiler = Utils.PathCombine(WixLocation, "candle.exe");
-            string wix = Utils.PathCombine(WixLocation, "wix.exe");
             string linker = Utils.PathCombine(WixLocation, "light.exe");
             string batchFile = path;
 
-            if ((Compiler.IsWix4 && !IO.File.Exists(wix)) ||
-                (!Compiler.IsWix4 && (!IO.File.Exists(compiler) || !IO.File.Exists(linker))))
+            if (!IO.File.Exists(compiler) && !IO.File.Exists(linker))
             {
                 Compiler.OutputWriteLine("Wix binaries cannot be found. Expected location is " + IO.Path.GetDirectoryName(compiler));
-                throw new ApplicationException("Wix tools cannot be found");
-            }
-
-            if (Compiler.IsWix4)
-            {
-                string wxsFile = BuildWxs(project, type);
-
-                string outDir = IO.Path.GetDirectoryName(wxsFile);
-                string msiFile = IO.Path.ChangeExtension(wxsFile, "." + type.ToString().ToLower());
-
-                string wixCmd = GenerateWixCommand(project, wxsFile, out string extensionDlls);
-
-                using (var sw = new IO.StreamWriter(batchFile))
-                {
-                    sw.WriteLine("echo off");
-                    // sw.WriteLine("@setlocal");
-                    // sw.WriteLine(wixLocationEnvVar);
-                    sw.WriteLine($"\"{wix}\" build {wixCmd} -o \"{outDir.PathJoin(msiFile)}\"");
-                    // sw.WriteLine("if ERRORLEVEL 1 @echo wix.exe failed & GOTO ERROR");
-                    // sw.WriteLine("@endlocal");
-                    // sw.WriteLine("EXIT /B 0");
-                    // sw.WriteLine(":ERROR");
-                    // sw.WriteLine("@endlocal");
-                    // sw.WriteLine("EXIT /B 1");
-                }
+                throw new ApplicationException("Wix compiler/linker cannot be found");
             }
             else
             {
@@ -728,32 +679,6 @@ This code was generated by WixSharp.
             IO.File.WriteAllLines(dest, content.ToArray());
         }
 
-        static string GenerateWixCommand(Project project, string wxsFile, out string extensionDlls)
-        {
-            // Debug.Assert(false);
-            // objFile = IO.Path.ChangeExtension(wxsFile, ".wixobj");
-
-            extensionDlls = project.WixExtensions
-                                   .Select(x => x.ExpandEnvVars().PathGetFullPath())
-                                   .Distinct()
-                                   .JoinBy(" ", dll => " -ext \"" + dll + "\"");
-
-            string wxsFiles = project.WxsFiles
-                                     .Select(x => x.ExpandEnvVars().PathGetFullPath())
-                                     .Distinct()
-                                     .JoinBy(" ", file => "\"" + file + "\"");
-
-            var candleOptions = WixOptions + " " + project.WixOptions;
-
-            var candleCmdLineParams = new StringBuilder();
-            candleCmdLineParams.AppendFormat("{0} {1} \"{2}\" ", candleOptions, extensionDlls, wxsFile);
-
-            if (wxsFiles.IsNotEmpty())
-                candleCmdLineParams.Append(wxsFiles);
-
-            return candleCmdLineParams.ToString().ExpandEnvVars();
-        }
-
         static string GenerateCandleCommand(Project project, string wxsFile, string outDir, out string objFile, out string extensionDlls)
         {
             // Debug.Assert(false);
@@ -1057,7 +982,7 @@ public StringWriterWithEncoding(Encoding encoding)
         static void IndjectCustomUI(Controls.CustomUI customUI, XDocument doc)
         {
             if (customUI != null)
-                doc.Root.Select(Compiler.ProductElementName).Add(customUI.ToXElement());
+                doc.Root.Select("Product").Add(customUI.ToXElement());
         }
 
         /// <summary>
@@ -1067,7 +992,7 @@ static void IndjectCustomUI(Controls.CustomUI customUI, XDocument doc)
         public static void DefaultWixSourceGeneratedHandler(XDocument doc)
         {
             XElement[] extract(string name)
-                => doc.Root.Select(Compiler.ProductElementName)
+                => doc.Root.Select("Product")
                       .Elements()
                       .Where(e =>
                           {
@@ -1090,13 +1015,13 @@ XElement[] extract(string name)
             foreach (var e in orderedElements)
             {
                 e.Remove();
-                doc.Root.Select(Compiler.ProductElementName).Add(e);
+                doc.Root.Select("Product").Add(e);
             }
         }
 
         static void ConvertMsiToMsm(XDocument doc)
         {
-            XElement[] extract(string name) => (from e in doc.Root.Select(Compiler.ProductElementName).Elements()
+            XElement[] extract(string name) => (from e in doc.Root.Select("Product").Elements()
                                                 where e.Name.LocalName == name
                                                 select e).ToArray();
 
@@ -1108,7 +1033,7 @@ XElement[] extract(string name) => (from e in doc.Root.Select(Compiler.ProductEl
             foreach (var e in elementsToRemove)
                 e.Remove();
 
-            XElement product = doc.Root.Select(Compiler.ProductElementName);
+            XElement product = doc.Root.Select("Product");
             product.Remove();
 
             XElement module = doc.Root.AddElement(new XElement("Module", product.Elements()));
@@ -1212,37 +1137,26 @@ public static XDocument GenerateWixProj(Project project)
                                                           .Select(x => x.StartsWith("xmlns:") ? x : "xmlns:" + x)
                                                           .ConcatItems(" ");
 
-            XDocument doc;
-            XElement product;
+            var wix3Namespace = "http://schemas.microsoft.com/wix/2006/wi";
+            var wix4Namespace = "http://wixtoolset.org/schemas/v4/wxs";
 
-            if (Compiler.IsWix4)
-            {
-                doc = XDocument.Parse($@"<?xml version=""1.0"" encoding=""utf-8""?>
-                                         <Wix xmlns=""http://wixtoolset.org/schemas/v4/wxs"" {extraNamespaces}>
-                                             <Package Compressed=""yes"">
-                                                <SummaryInformation Codepage=""{project.Codepage}"" />
-                                             </Package>
-                                         </Wix>");
+            var wixNamespace = Compiler.IsWix4 ? wix4Namespace : wix3Namespace;
+
+            XDocument doc = XDocument.Parse(
+                    @"<?xml version=""1.0"" encoding=""utf-8""?>
+                      <Wix " + $"xmlns=\"{wixNamespace}\" {extraNamespaces}" + @">
+                          <Product>
+                              <Package " + $"InstallerVersion=\"{project.InstallerVersion}\"" + @" Compressed=""yes""/>
+                          </Product>
+                      </Wix>");
 
-                product = doc.Root.Select("Package"); // in WiX v4 `Product` is merged with `Package`
-                product.SetAttribute("ProductCode", project.ProductId);
-            }
-            else
-            {
-                doc = XDocument.Parse($@"<?xml version=""1.0"" encoding=""utf-8""?>
-                                         <Wix xmlns=""http://schemas.microsoft.com/wix/2006/wi"" {extraNamespaces}>
-                                             <Product>
-                                                 <Package Compressed=""yes""/>
-                                             </Product>
-                                         </Wix>");
 
-                product = doc.Root.Select("Product")
-                                  .SetAttribute("Codepage", project.Codepage)
-                                  .SetAttribute("id", project.ProductId);
-            }
 
-            product.SetAttribute("Name", project.Name)
+            XElement product = doc.Root.Select("Product");
+            product.SetAttribute("Id", project.ProductId)
+                   .SetAttribute("Name", project.Name)
                    .SetAttribute("Language", project.Language.FirstLcid())
+                   .SetAttribute("Codepage", project.Codepage)
                    .SetAttribute("Version", project.Version)
                    .SetAttribute("UpgradeCode", project.UpgradeCode);
 
@@ -1251,18 +1165,15 @@ public static XDocument GenerateWixProj(Project project)
 
             product.AddAttributes(project.Attributes);
 
-            XElement package = doc.Root.Select("Package");
+            XElement package = product.Select("Package");
 
             package.SetAttribute("Description", project.Description)
                    .SetAttribute("Platform", project.Platform)
+                   .SetAttribute("SummaryCodepage", project.Codepage)
                    .SetAttribute("InstallPrivileges", project.InstallPrivileges)
-                   .SetAttribute("InstallerVersion", project.InstallerVersion)
                    .SetAttribute("InstallScope", project.InstallScope);
 
-            if (!Compiler.IsWix4)
-                package.SetAttribute("SummaryCodepage", project.Codepage);
-
-            if (!project.SuppressSettingPackageLanguages && !Compiler.IsWix4)
+            if (!project.SuppressSettingPackageLanguages)
                 package.SetAttribute("Languages", project.Language.ToLcidList());
 
             if (project.EmitConsistentPackageId)
@@ -1342,11 +1253,7 @@ public static XDocument GenerateWixProj(Project project)
                            .SetAttribute("Value", installDirId);
                 }
 
-                // to avoid "error WIX0094: The identifier 'WixUI:WixUI_Minimal' is inaccessible due to its protection level."
-                if (!Compiler.IsWix4 || project.UI != WUI.WixUI_Minimal)
-                    product.AddElement("UIRef", $"Id={project.UI}");
-
-
+                product.AddElement("UIRef", $"Id={project.UI}");
                 product.AddElement("UIRef", "Id=WixUI_ErrorProgressText");
 
                 project.Include(WixExtension.UI);
@@ -1863,7 +1770,7 @@ static void ProcessDirectoryFiles(Dir wDir, Project wProject, Dictionary<Feature
                         {
                             var icon = new IconFile { SourceFile = wFileAssociation.Icon };
 
-                            progId.Parent(Compiler.ProductElementName)
+                            progId.Parent("Product")
                                   .AddElement(icon.ToXElement("Icon"));
 
                             progId.SetAttribute("Icon", icon.Id);
@@ -2138,7 +2045,7 @@ static void ProcessMergeModules(Dir wDir, XElement dirItem, Dictionary<Feature,
         {
             foreach (Merge msm in wDir.MergeModules)
             {
-                XElement product = dirItem.Parent(Compiler.ProductElementName);
+                XElement product = dirItem.Parent("Product");
 
                 //note Wix# expects package.Attribute("Languages") to have a single value (yes it is a temporary limitation)
                 string language = product.Select("Package").Attribute("Languages").Value;
@@ -2494,10 +2401,10 @@ static void InsertWebSite(WebSite webSite, string dirID, XElement parent, Projec
                         string bynaryPath = project.SourceBaseDir.PathJoin(binary.Name);
 
                         parent.Document
-                              .FindFirst(Compiler.ProductElementName)
+                              .FindFirst("Product")
                               .AddElement("Binary", $"Id={binary.Id};SourceFile={bynaryPath}");
 
-                        certificate.SetAttribute(CABinarykeyAttrName, binary.Id);
+                        certificate.SetAttribute("BinaryKey", binary.Id);
                     }
                 }
 
@@ -2515,7 +2422,7 @@ static void InsertIISElements(XElement dirItem, XElement component, IISVirtualDi
             XNamespace ns = "http://schemas.microsoft.com/wix/IIsExtension";
 
             string dirID = dirItem.Attribute("Id").Value;
-            var xProduct = component.Parent(Compiler.ProductElementName);
+            var xProduct = component.Parent("Product");
 
             var uniqueProductWebSites = new List<WebSite>();
             var uniqueComponentWebSites = new List<WebSite>();
@@ -2716,8 +2623,6 @@ static void ProcessCustomActions(Project wProject, XElement product)
         {
             foreach (Action wAction in wProject.Actions)
             {
-                object wActionCondition = wAction.ToXmlCondition();
-
                 string step = wAction.Step.ToString();
                 string roollbackActionId = wAction.Id + "_Rollback";
 
@@ -2779,7 +2684,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                             .AddAttributes(wAction.Attributes));
 
                     sequences.ForEach(sequence =>
-                        sequence.Add(new XElement("Custom", wActionCondition,
+                        sequence.Add(new XElement("Custom", wAction.Condition.ToXValue(),
                                          new XAttribute("Action", actionId),
                                          sequenceNumberAttr)));
                 }
@@ -2788,7 +2693,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     var wScriptAction = (ScriptFileAction)wAction;
 
                     sequences.ForEach(sequence =>
-                         sequence.Add(new XElement("Custom", wActionCondition,
+                         sequence.Add(new XElement("Custom", wAction.Condition.ToXValue(),
                                           new XAttribute("Action", wAction.Id),
                                           sequenceNumberAttr)));
 
@@ -2798,7 +2703,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
 
                     product.Add(new XElement("CustomAction",
                                     new XAttribute("Id", wAction.Id),
-                                    new XAttribute(CABinarykeyAttrName, wAction.Name.Expand() + "_File"),
+                                    new XAttribute("BinaryKey", wAction.Name.Expand() + "_File"),
                                     new XAttribute("VBScriptCall", wScriptAction.Procedure))
                                     .SetAttribute("Return", wAction.Return)
                                     .SetAttribute("Impersonate", wAction.Impersonate)
@@ -2808,13 +2713,13 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     if ((wScriptAction.Execute == Execute.deferred) && wScriptAction.Rollback.IsNotEmpty())
                     {
                         sequences.ForEach(sequence =>
-                            sequence.Add(new XElement("Custom", wActionCondition,
+                            sequence.Add(new XElement("Custom", wScriptAction.Condition.ToXValue(),
                                 new XAttribute("Action", roollbackActionId),
                                 new XAttribute("Before", wAction.Id))));
 
                         product.AddElement(new XElement("CustomAction",
                                 new XAttribute("Id", roollbackActionId),
-                                new XAttribute(CABinarykeyAttrName, wAction.Name.Expand() + "_File"),
+                                new XAttribute("BinaryKey", wAction.Name.Expand() + "_File"),
                                 new XAttribute("VBScriptCall", wScriptAction.RollbackArg))
                             .SetAttribute("Return", wAction.Return)
                             .SetAttribute("Impersonate", wAction.Impersonate)
@@ -2827,8 +2732,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     var wScriptAction = (ScriptAction)wAction;
 
                     sequences.ForEach(sequence =>
-                        sequence.Add(new XElement("Custom",
-                                       wAction.ToXmlCondition(),
+                        sequence.Add(new XElement("Custom", wAction.Condition.ToXValue(),
                                        new XAttribute("Action", wAction.Id),
                                        sequenceNumberAttr)));
 
@@ -2844,7 +2748,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     if ((wScriptAction.Execute == Execute.deferred) && wScriptAction.Rollback.IsNotEmpty())
                     {
                         sequences.ForEach(sequence =>
-                            sequence.Add(new XElement("Custom", wActionCondition,
+                            sequence.Add(new XElement("Custom", wScriptAction.Condition.ToXValue(),
                                 new XAttribute("Action", roollbackActionId),
                                 new XAttribute("Before", wAction.Id))));
 
@@ -2928,13 +2832,13 @@ static void ProcessCustomActions(Project wProject, XElement product)
                         }
                     }
 
-                    sequences.ForEach(item => item.Add(new XElement("Custom", wActionCondition,
+                    sequences.ForEach(item => item.Add(new XElement("Custom", wAction.Condition.ToXValue(),
                                                            new XAttribute("Action", wAction.Id),
                                                            sequenceNumberAttr)));
 
                     product.Add(new XElement("CustomAction",
                                     new XAttribute("Id", wAction.Id),
-                                    new XAttribute(CABinarykeyAttrName, bynaryKey),
+                                    new XAttribute("BinaryKey", bynaryKey),
                                     new XAttribute("DllEntry", wManagedAction.MethodName))
                                     .SetAttribute("Return", wAction.Return)
                                     .SetAttribute("Impersonate", wAction.Impersonate)
@@ -2956,14 +2860,14 @@ static void ProcessCustomActions(Project wProject, XElement product)
                         }
 
                         sequences.ForEach(sequence =>
-                            sequence.Add(new XElement("Custom", wActionCondition,
+                            sequence.Add(new XElement("Custom", wAction.Condition.ToXValue(),
                                 new XAttribute("Action", roollbackActionId),
                                 new XAttribute("Before", wAction.Id))));
 
                         product.AddElement(
                             new XElement("CustomAction",
                                     new XAttribute("Id", roollbackActionId),
-                                    new XAttribute(CABinarykeyAttrName, bynaryKey),
+                                    new XAttribute("BinaryKey", bynaryKey),
                                     new XAttribute("DllEntry", wManagedAction.Rollback))
                                 .SetAttribute("Return", wAction.Return)
                                 .SetAttribute("Impersonate", wAction.Impersonate)
@@ -2975,7 +2879,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                 {
                     var wCustomActionRef = (CustomActionRef)wAction;
                     sequences.ForEach(sequence =>
-                        sequence.Add(new XElement("Custom", wActionCondition,
+                        sequence.Add(new XElement("Custom", wCustomActionRef.Condition.ToXValue(),
                             new XAttribute("Action", wCustomActionRef.Id),
                             new XAttribute(wCustomActionRef.When.ToString(), wCustomActionRef.Step))));
 
@@ -2998,7 +2902,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     product.AddElement(
                         new XElement("CustomAction")
                             .SetAttribute("Id", cmdLineActionId)
-                            .SetAttribute(CABinarykeyAttrName, "WixCA")
+                            .SetAttribute("BinaryKey", "WixCA")
                             .SetAttribute("DllEntry", quietExecAction.ActionName)
                             .SetAttribute("Return", wAction.Return)
                             .SetAttribute("Impersonate", wAction.Impersonate)
@@ -3007,13 +2911,13 @@ static void ProcessCustomActions(Project wProject, XElement product)
 
                     sequences.ForEach(sequence =>
                         sequence.Add(
-                            new XElement("Custom", wActionCondition,
+                            new XElement("Custom", wAction.Condition.ToXValue(),
                                 new XAttribute("Action", setCmdLineActionId),
                                 sequenceNumberAttr)));
 
                     sequences.ForEach(sequence =>
                         sequence.Add(
-                            new XElement("Custom", wActionCondition,
+                            new XElement("Custom", wAction.Condition.ToXValue(),
                                 new XAttribute("Action", cmdLineActionId),
                                 new XAttribute("After", setCmdLineActionId))));
 
@@ -3026,14 +2930,14 @@ static void ProcessCustomActions(Project wProject, XElement product)
                             new XAttribute("Value", "\"" + quietExecAction.Rollback.ExpandCommandPath() + "\" " + quietExecAction.RollbackArg.ExpandCommandPath())));
 
                         sequences.ForEach(sequence =>
-                            sequence.Add(new XElement("Custom", wActionCondition,
+                            sequence.Add(new XElement("Custom", wAction.Condition.ToXValue(),
                                 new XAttribute("Action", roollbackActionId),
                                 new XAttribute("Before", wAction.Id))));
 
                         product.AddElement(
                             new XElement("CustomAction")
                                 .SetAttribute("Id", roollbackActionId)
-                                .SetAttribute(CABinarykeyAttrName, "WixCA")
+                                .SetAttribute("BinaryKey", "WixCA")
                                 .SetAttribute("DllEntry", quietExecAction.ActionName)
                                 .SetAttribute("Return", wAction.Return)
                                 .SetAttribute("Impersonate", wAction.Impersonate)
@@ -3049,7 +2953,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
 
                     sequences.ForEach(sequence =>
                         sequence.Add(
-                            new XElement("Custom", wActionCondition,
+                            new XElement("Custom", wAction.Condition.ToXValue(),
                                 new XAttribute("Action", wAction.Id),
                                 sequenceNumberAttr)));
 
@@ -3066,7 +2970,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     if ((fileAction.Execute == Execute.deferred) && fileAction.Rollback.IsNotEmpty())
                     {
                         sequences.ForEach(sequence =>
-                            sequence.Add(new XElement("Custom", wActionCondition,
+                            sequence.Add(new XElement("Custom", wAction.Condition.ToXValue(),
                                 new XAttribute("Action", roollbackActionId),
                                 new XAttribute("Before", wAction.Id))));
 
@@ -3089,7 +2993,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
 
                     sequences.ForEach(sequence =>
                         sequence.Add(
-                            new XElement("Custom", wActionCondition,
+                            new XElement("Custom", wAction.Condition.ToXValue(),
                                 new XAttribute("Action", wAction.Id),
                                 sequenceNumberAttr)));
 
@@ -3097,7 +3001,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                         new XElement("CustomAction",
                                 new XAttribute("Id", wAction.Id),
                                 new XAttribute("ExeCommand", binaryAction.Args.ExpandCommandPath()),
-                                new XAttribute(CABinarykeyAttrName, binaryAction.Key))
+                                new XAttribute("BinaryKey", binaryAction.Key))
                             .SetAttribute("Return", wAction.Return)
                             .SetAttribute("Impersonate", wAction.Impersonate)
                             .SetAttribute("Execute", wAction.Execute)
@@ -3106,7 +3010,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     if ((binaryAction.Execute == Execute.deferred) && binaryAction.Rollback.IsNotEmpty())
                     {
                         sequences.ForEach(sequence =>
-                            sequence.Add(new XElement("Custom", wActionCondition,
+                            sequence.Add(new XElement("Custom", binaryAction.Condition.ToXValue(),
                                 new XAttribute("Action", roollbackActionId),
                                 new XAttribute("Before", wAction.Id))));
 
@@ -3116,7 +3020,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                                     new XAttribute("ExeCommand", binaryAction.RollbackArg.IsEmpty()
                                         ? binaryAction.Args.ExpandCommandPath()
                                         : binaryAction.RollbackArg.ExpandCommandPath()),
-                                new XAttribute(CABinarykeyAttrName, binaryAction.Rollback))
+                                new XAttribute("BinaryKey", binaryAction.Rollback))
                                 .SetAttribute("Return", wAction.Return)
                                 .SetAttribute("Impersonate", wAction.Impersonate)
                                 .SetAttribute("Execute", Execute.rollback)
@@ -3129,7 +3033,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
 
                     sequences.ForEach(sequence =>
                         sequence.Add(
-                            new XElement("Custom", wActionCondition,
+                            new XElement("Custom", fileAction.Condition.ToXValue(),
                                 new XAttribute("Action", wAction.Id),
                                 sequenceNumberAttr)));
 
@@ -3150,7 +3054,7 @@ static void ProcessCustomActions(Project wProject, XElement product)
                     if ((fileAction.Execute == Execute.deferred) && fileAction.Rollback.IsNotEmpty())
                     {
                         sequences.ForEach(sequence =>
-                            sequence.Add(new XElement("Custom", wActionCondition,
+                            sequence.Add(new XElement("Custom", fileAction.Condition.ToXValue(),
                                 new XAttribute("Action", roollbackActionId),
                                 new XAttribute("Before", wAction.Id))));
 
@@ -3313,22 +3217,8 @@ static void PackageManagedAsm(string asm, string nativeDll, string[] refAssembli
             if (platform.HasValue && platform.Value == Platform.x64)
                 platformDir = "x64";
 
-            string makeSfxCA;
-            string sfxcaDll;
-            string dtfWinInstaller;
-
-            if (Compiler.IsWix4) // zos
-            {
-                makeSfxCA = @"C:\Users\oleg.shilo\.nuget\packages\wixtoolset.dtf.customaction\4.0.0\tools\WixToolset.Dtf.MakeSfxCA.exe";
-                sfxcaDll = $@"C:\Users\oleg.shilo\.nuget\packages\wixtoolset.dtf.customaction\4.0.0\tools\{platformDir}\SfxCA.dll";
-                dtfWinInstaller = @"C:\Users\oleg.shilo\source\repos\CustomAction1\CustomAction1\publish\WixToolset.Dtf.WindowsInstaller.dll";
-            }
-            else
-            {
-                makeSfxCA = Utils.PathCombine(WixSdkLocation, @"MakeSfxCA.exe");
-                sfxcaDll = Utils.PathCombine(WixSdkLocation, platformDir + "\\sfxca.dll");
-                dtfWinInstaller = WixSdkLocation.PathCombine("WixToolset.Dtf.WindowsInstaller.dll");
-            }
+            var makeSfxCA = Utils.PathCombine(WixSdkLocation, @"MakeSfxCA.exe");
+            var sfxcaDll = Utils.PathCombine(WixSdkLocation, platformDir + "\\sfxca.dll");
 
             outDir = IO.Path.GetFullPath(outDir);
 
@@ -3418,7 +3308,10 @@ static void PackageManagedAsm(string asm, string nativeDll, string[] refAssembli
                         (pdbFileArgument ?? " ") +
                         referencedAssemblies;
 
-            makeSfxCA_args += $" \"{dtfWinInstaller}\"";
+            if (IsWix4)
+                makeSfxCA_args += $" \"{WixSdkLocation.PathCombine("WixToolset.Dtf.WindowsInstaller.dll")}\"";
+            else
+                makeSfxCA_args += $" \"{WixSdkLocation.PathCombine("Microsoft.Deployment.WindowsInstaller.dll")}\"";
 
             ProjectValidator.ValidateCAAssembly(asmFile);
 #if DEBUG
@@ -3447,25 +3340,10 @@ static void PackageManagedAsm(string asm, string nativeDll, string[] refAssembli
         /// <value>
         ///   <c>true</c> if this instance is wix4; otherwise, <c>false</c>.
         /// </value>
-        public static bool IsWix4 { get; set; }
-
-        /// <summary>
-        /// This property contains the name of the logical 'Product' XML element. The need for this property arises 
-        /// from the changes in WiX v4.0 where 'Product' element was merged with "Package" element.
-        /// <p>ThiOn WiX v4.* it is <c>Package</c></p>
-        /// <p>On WiX v3.* it is <c>Product</c></p>
-        /// <p>On WiX v4.* it is <c>Package</c></p>
-        /// </summary>
-        public static string ProductElementName => Compiler.IsWix4 ? "Package" : "Product";
-
-        /// <summary>
-        /// This property contains the name of the logical 'BinaryKey' XML atribute of the Custom Action element. The need for this property arises 
-        /// from the changes in WiX v4.0 where 'BinaryKey' attribute was been renamed into "BinaryRef".
-        /// <p>ThiOn WiX v4.* it is <c>Package</c></p>
-        /// <p>On WiX v3.* it is <c></c></p>
-        /// <p>On WiX v4.* it is <c></c></p>
-        /// </summary>
-        internal static string CABinarykeyAttrName => Compiler.IsWix4 ? "BinaryRef" : "BinaryKey";
+        public static bool IsWix4
+        {
+            get => false;
+        }
 
         /// <summary>
         /// Gets list of the mapped WiX constants.
diff --git a/Source/src/WixSharp/Extensions.cs b/Source/src/WixSharp/Extensions.cs
index 35e42123..254cf52f 100644
--- a/Source/src/WixSharp/Extensions.cs
+++ b/Source/src/WixSharp/Extensions.cs
@@ -5,7 +5,6 @@
 using System.Data;
 using System.Diagnostics;
 using System.Drawing;
-using static System.Environment;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -17,15 +16,11 @@
 using System.Text.RegularExpressions;
 using System.Windows.Forms;
 using System.Xml.Linq;
+using Microsoft.Deployment.WindowsInstaller;
 using Microsoft.Tools.WindowsInstallerXml.Bootstrapper;
 using Microsoft.Win32;
 using WixSharp.CommonTasks;
 using static WixSharp.SetupEventArgs;
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 
 using IO = System.IO;
 
@@ -661,9 +656,9 @@ public static XElement CopyAttributeFrom(this XElement dest, XElement src, strin
         /// <para>
         /// This method is nothing else but a 'syntactic sugar' method, which wraps the following code:
         /// <code>
-        ///document.Root.Select(Compiler.ProductElementName)
+        ///document.Root.Select("Product")
         ///             .Add(XDocument.Load(wxsFile)
-        ///             .Root.Select(Compiler.ProductElementName).Elements());
+        ///             .Root.Select("Product").Elements());
         /// </code>
         /// </para>
         /// <example>The following is an example of using InjectWxs.
@@ -689,9 +684,9 @@ public static XElement CopyAttributeFrom(this XElement dest, XElement src, strin
         /// <returns></returns>
         public static XDocument InjectWxs(this XDocument document, string wxsFile)
         {
-            document.Root.Select(Compiler.ProductElementName)
+            document.Root.Select("Product")
                          .Add(XDocument.Load(wxsFile)
-                                       .Root.Select(Compiler.ProductElementName).Elements());
+                                       .Root.Select("Product").Elements());
             return document;
         }
 
@@ -2810,7 +2805,7 @@ public static bool IsCancelled(this Session session)
         {
             try
             {
-                session.Message(WixToolset.Dtf.WindowsInstaller.InstallMessage.ActionData, new Record());
+                session.Message(Microsoft.Deployment.WindowsInstaller.InstallMessage.ActionData, new Record());
             }
             catch (InstallCanceledException)
             {
@@ -3898,117 +3893,6 @@ public XmlAttribute(string name, bool isCData)
     /// </summary>
     public static class ProcessExtensions
     {
-        // public static string[] FindAssembliesOf(IEnumerable<string> packages)
-        //         {
-        //             // TODO
-        //             // - create a project template based on "dotnet new classlib" output
-        //             // - analyse only directories that are listed in `*.nuget.cache` file (e.g. test\obj\project.nuget.cache)
-
-        //             var result = new List<string>();
-
-        //             var projectDir = SpecialFolder.LocalApplicationData.GetPath("Temp", "csscript.core", "nuget", Guid.NewGuid().ToString());
-        //             Directory.CreateDirectory(projectDir);
-
-        //             var packagsSection = "";
-        //             var restoreArgs = "";
-
-        //             try
-        //             {
-        //                 var projectFile = projectDir.PathJoin("nuget.ref.csproj");
-
-        //                 File.WriteAllText(projectFile, $@"<Project Sdk=""Microsoft.NET.Sdk"">
-        //   <PropertyGroup>
-        //     <TargetFramework>net472</TargetFramework>
-        //   </PropertyGroup>
-
-        //   <ItemGroup>
-        //     <Content Include=""CustomAction.config"" CopyToOutputDirectory=""PreserveNewest"" />
-        //   </ItemGroup>
-
-        //   <ItemGroup>
-        //     <PackageReference Include=""WixToolset.Dtf.CustomAction"" Version=""*"" />
-        //     <PackageReference Include=""WixToolset.Dtf.WindowsInstaller"" Version=""*"" />
-        //   </ItemGroup>
-        // </Project>");
-
-        //                 packages = packages.OrderBy(x => x).ToArray();
-
-        //                 var sw = Stopwatch.StartNew();
-        //                 Console.WriteLine("Restoring packages...");
-        //                 // Console.WriteLine(packages.JoinBy(NewLine));
-
-        //                 var p = new Process();
-        //                 p.StartInfo.FileName = "dotnet";
-        //                 p.StartInfo.Arguments = "restore " + restoreArgs.Trim();
-        //                 p.StartInfo.WorkingDirectory = projectDir;
-        //                 p.StartInfo.RedirectStandardOutput = true;
-        //                 p.Start();
-        //                 p.WaitForExit();
-
-        //                 p = new Process();
-        //                 p.StartInfo.FileName = "dotnet";
-        //                 p.StartInfo.Arguments = "publish --no-restore -o ./publish";
-        //                 p.StartInfo.WorkingDirectory = projectDir;
-        //                 p.StartInfo.RedirectStandardOutput = true;
-        //                 p.Start();
-        //                 p.WaitForExit();
-
-        //                 var allRefAssemblies = Directory.GetFiles(Path.Combine(projectDir, "publish"), "*.dll")
-        //                                            .Concat(
-        //                                        Directory.GetFiles(Path.Combine(projectDir, "publish"), "*.exe"))
-        //                                            .Where(x => !x.EndsWith("nuget.ref.dll"))
-        //                                            .OrderBy(x => x);
-
-        //                 bool isSameData(byte[] a, byte[] b)
-        //                 {
-        //                     if (a.Length == b.Length)
-        //                     {
-        //                         for (int i = 0; i < a.Length; i++)
-        //                             if (a[i] != b[i])
-        //                                 return false;
-        //                         return true;
-        //                     }
-        //                     else
-        //                         return false;
-        //                 }
-
-        //                 // Console.WriteLine("    " + sw.Elapsed.ToString());
-        //                 sw.Restart();
-        //                 Console.WriteLine("Mapping packages to assemblies1111...");
-        //                 // Debug.Assert(false);
-
-        //                 foreach (var x in allRefAssemblies)
-        //                 {
-        //                     var packageName = Path.GetFileNameWithoutExtension(x);
-
-        //                     var refAssemblyVersion = FileVersionInfo.GetVersionInfo(x).FileVersion;
-        //                     var refAssemblySize = new FileInfo(x).Length;
-        //                     byte[] refAssemblyBytes = File.ReadAllBytes(x);
-
-        //                     var matchingAssemblies = Directory
-        //                             // .GetDirectories(nugetRepo, $"{packageName}*") // quicker but less reliable as the package name may not be the same as the assembly name. IE `ICSharpCode.SharpZipLib.dll` vs `SharpZipLib.dll`
-        //                             .GetDirectories(NuGetCache, $"*")
-        //                             .SelectMany(d => Directory
-        //                                                  .GetFiles(d, Path.GetFileName(x), SearchOption.AllDirectories)
-        //                                                  .Where(f =>
-        //                                                         refAssemblyVersion == FileVersionInfo.GetVersionInfo(f).FileVersion
-        //                                                         && refAssemblySize == new FileInfo(f).Length
-        //                                                         && isSameData(refAssemblyBytes, File.ReadAllBytes(f))
-        //                                                        ));
-
-        //                     var assembly = matchingAssemblies.FirstOrDefault() ?? $"{packageName} - not found";
-        //                     result.Add(assembly);
-        //                 }
-        //                 // Console.WriteLine("    " + sw.Elapsed.ToString());
-        //             }
-        //             finally
-        //             {
-        //                 try { Directory.Delete(projectDir, true); }
-        //                 catch { }
-        //             }
-        //             return result.ToArray();
-        //         }
-
         /// <summary>
         /// Starts a process resource by specifying the name of an application and a set of
         /// command-line arguments, and associates the resource with a new
diff --git a/Source/src/WixSharp/Feature.cs b/Source/src/WixSharp/Feature.cs
index 075a611f..c66286c7 100644
--- a/Source/src/WixSharp/Feature.cs
+++ b/Source/src/WixSharp/Feature.cs
@@ -223,7 +223,7 @@ public Feature(string name, string description, bool isEnabled, bool allowChange
         /// <summary>
         /// The default path of the feature <c>ConfigurableDirectory</c>. If set to non-empty string, MSI runtime will place
         /// <c>Configure</c> button for the feature in the <c>Feature Selection</c> dialog.
-        /// <para>Specify the Id of a Directory that can be configured by the user at installation
+        /// <para>Specify the Id of a Directory that can be configured by the user at installation 
         /// time. This identifier must be a public property and therefore completely uppercase. </para>
         /// </summary>
         public string ConfigurableDir = "";
@@ -274,17 +274,13 @@ internal XElement ToXml()
             var element = new XElement("Feature");
             element.SetAttribute("Id", Id)
                    .SetAttribute("Title", Name)
+                   .SetAttribute("Absent", AllowChange ? "allow" : "disallow")
                    .SetAttribute("Level", IsEnabled ? "1" : "2")
                    .SetAttribute("Description", Description)
                    .SetAttribute("Display", Display)
                    .SetAttribute("ConfigurableDirectory", ConfigurableDir)
                    .AddAttributes(Attributes);
 
-            if (Compiler.IsWix4)
-                element.SetAttribute("AllowAbsent", AllowChange.ToYesNo());
-            else
-                element.SetAttribute("Absent", AllowChange ? "allow" : "disallow");
-
             if (Condition != null)
                 element.Add( //intentionally leaving out AddAttributes(...) as Level is the only valid attribute on */Feature/Condition
                     new XElement("Condition",
diff --git a/Source/src/WixSharp/InternetShortcut.cs b/Source/src/WixSharp/InternetShortcut.cs
index c7b2a27c..80ffdece 100644
--- a/Source/src/WixSharp/InternetShortcut.cs
+++ b/Source/src/WixSharp/InternetShortcut.cs
@@ -7,17 +7,13 @@
 using System.Security.Principal;
 using System.Text;
 using System.Xml.Linq;
+using Microsoft.Deployment.WindowsInstaller;
 using Microsoft.Win32;
 using System.Globalization;
 using System.Reflection;
 using System.Text.RegularExpressions;
 using static WixSharp.SetupEventArgs;
 using WixSharp.CommonTasks;
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 
 namespace WixSharp
 {
diff --git a/Source/src/WixSharp/ManagedAction.cs b/Source/src/WixSharp/ManagedAction.cs
index 960a64e4..a7239383 100644
--- a/Source/src/WixSharp/ManagedAction.cs
+++ b/Source/src/WixSharp/ManagedAction.cs
@@ -28,11 +28,7 @@ THE SOFTWARE.
 using System.Diagnostics;
 using System.Linq;
 using System.Linq.Expressions;
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 
 namespace WixSharp
 {
diff --git a/Source/src/WixSharp/ManagedProject/Interfaces.cs b/Source/src/WixSharp/ManagedProject/Interfaces.cs
index d32c8104..e684c378 100644
--- a/Source/src/WixSharp/ManagedProject/Interfaces.cs
+++ b/Source/src/WixSharp/ManagedProject/Interfaces.cs
@@ -1,11 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 using Reflection = System.Reflection;
 
 #pragma warning disable 1591
diff --git a/Source/src/WixSharp/ManagedProject/ManagedProject.cs b/Source/src/WixSharp/ManagedProject/ManagedProject.cs
index 859d44b9..8a9fc072 100644
--- a/Source/src/WixSharp/ManagedProject/ManagedProject.cs
+++ b/Source/src/WixSharp/ManagedProject/ManagedProject.cs
@@ -6,13 +6,8 @@
 using System.Linq.Expressions;
 using System.Reflection;
 using System.Text;
-using WixSharp.CommonTasks;
-
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
+using WixSharp.CommonTasks;
 
 using IO = System.IO;
 
diff --git a/Source/src/WixSharp/ManagedProject/ManagedProjectActions.cs b/Source/src/WixSharp/ManagedProject/ManagedProjectActions.cs
index b08960ba..7758aea8 100644
--- a/Source/src/WixSharp/ManagedProject/ManagedProjectActions.cs
+++ b/Source/src/WixSharp/ManagedProject/ManagedProjectActions.cs
@@ -4,12 +4,8 @@
 using System.Linq.Expressions;
 using System.Runtime.InteropServices;
 using System.Windows.Forms;
-using WixSharp.CommonTasks;
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
+using WixSharp.CommonTasks;
 
 namespace WixSharp
 {
diff --git a/Source/src/WixSharp/ManagedProject/SetupEventArgs.cs b/Source/src/WixSharp/ManagedProject/SetupEventArgs.cs
index e619ca74..188b5ebc 100644
--- a/Source/src/WixSharp/ManagedProject/SetupEventArgs.cs
+++ b/Source/src/WixSharp/ManagedProject/SetupEventArgs.cs
@@ -2,13 +2,8 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Security.Principal;
-using WixSharp.CommonTasks;
-
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
+using WixSharp.CommonTasks;
 
 namespace WixSharp
 {
diff --git a/Source/src/WixSharp/NativeImage.cs b/Source/src/WixSharp/NativeImage.cs
index e8fd3844..f39b041a 100644
--- a/Source/src/WixSharp/NativeImage.cs
+++ b/Source/src/WixSharp/NativeImage.cs
@@ -7,15 +7,11 @@
 using System.Security.Principal;
 using System.Text;
 using System.Xml.Linq;
+using Microsoft.Deployment.WindowsInstaller;
 using Microsoft.Win32;
 using System.Globalization;
 using System.Reflection;
 using System.Text.RegularExpressions;
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 using static WixSharp.SetupEventArgs;
 
 namespace WixSharp
diff --git a/Source/src/WixSharp/ProjectValidator.cs b/Source/src/WixSharp/ProjectValidator.cs
index 81066b00..d2ac94e2 100644
--- a/Source/src/WixSharp/ProjectValidator.cs
+++ b/Source/src/WixSharp/ProjectValidator.cs
@@ -36,12 +36,9 @@ THE SOFTWARE.
 using System.Linq;
 using System.Reflection;
 using System.Text;
-using WixSharp.CommonTasks;
-#if WIX3
 using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
+using WixSharp.CommonTasks;
+
 using IO = System.IO;
 using Reflection = System.Reflection;
 
diff --git a/Source/src/WixSharp/ResilientPackage.cs b/Source/src/WixSharp/ResilientPackage.cs
index d3ed7502..dec2de32 100644
--- a/Source/src/WixSharp/ResilientPackage.cs
+++ b/Source/src/WixSharp/ResilientPackage.cs
@@ -2,15 +2,9 @@
 using System.ComponentModel;
 using System.Runtime.InteropServices;
 using System.Text;
+using Microsoft.Deployment.WindowsInstaller;
 using WixSharp.CommonTasks;
 using WixSharp.Utilities;
-
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
-
 using IO = System.IO;
 
 namespace WixSharp
@@ -71,7 +65,7 @@ public static void EnableResilientPackage(this Project project, string resilient
                     Return.check,
                     When.Before, Step.PublishProduct,
                     Condition.NOT_Installed)
-                              );
+            );
 
             var assembly = typeof(ResilientPackage).Assembly.Location;
 
@@ -99,7 +93,7 @@ public static void EnableResilientPackage(this Project project, string resilient
                 {
                     UsesProperties = $"UserSID,OriginalDatabase,ALLUSERS,{WIXSHARP_RESILIENT_SOURCE_DIR}"
                 }
-                              );
+            );
         }
 
         /// <summary>
diff --git a/Source/src/WixSharp/UACRevealer.cs b/Source/src/WixSharp/UACRevealer.cs
index c0ea43a0..901e38ac 100644
--- a/Source/src/WixSharp/UACRevealer.cs
+++ b/Source/src/WixSharp/UACRevealer.cs
@@ -11,14 +11,10 @@
 using System.Windows.Forms;
 using System.Xml.Linq;
 using System.Xml.XPath;
+using Microsoft.Deployment.WindowsInstaller;
 using Microsoft.Win32;
 using WixSharp;
 using WixSharp.Controls;
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
 
 namespace WixSharp.CommonTasks
 {
diff --git a/Source/src/WixSharp/UninstallFullUI.cs b/Source/src/WixSharp/UninstallFullUI.cs
index 47bafd15..a2c7fdde 100644
--- a/Source/src/WixSharp/UninstallFullUI.cs
+++ b/Source/src/WixSharp/UninstallFullUI.cs
@@ -1,13 +1,8 @@
 using System.Linq;
+using Microsoft.Deployment.WindowsInstaller;
 using Microsoft.Win32;
 using WixSharp.CommonTasks;
 
-#if WIX3
-using Microsoft.Deployment.WindowsInstaller;
-#else
-using WixToolset.Dtf.WindowsInstaller;
-#endif
-
 namespace WixSharp
 {
     /// <summary>
@@ -84,7 +79,7 @@ public static void EnableUninstallFullUI(this Project project, string displayIco
                 {
                     return;
                 }
-
+                
                 var comp = doc.FindAll("RegistryValue")
                     .First(x => x.HasAttribute("Id", "WixSharp_RegValue_DisplayIcon"))
                     .Parent
diff --git a/Source/src/WixSharp/WixExtension.cs b/Source/src/WixSharp/WixExtension.cs
index c27722d1..4252d777 100644
--- a/Source/src/WixSharp/WixExtension.cs
+++ b/Source/src/WixSharp/WixExtension.cs
@@ -199,11 +199,7 @@ public static string GetNamespaceDeclaration(string prefix, string @namespace)
         /// <summary>
         /// Well-known Wix Extension UI
         /// </summary>
-#if WIX3
         public static WixExtension UI = new WixExtension("%WixLocation%\\WixUIExtension.dll", null, null);
-#else
-        public static WixExtension UI = new WixExtension(@"C:\Users\oleg.shilo\.nuget\packages\wixtoolset.ui.wixext\4.0.0\wixext4\WixToolset.UI.wixext.dll", null, null);
-#endif
     }
 
     /// <summary>
diff --git a/Source/src/WixSharp/WixProject.cs b/Source/src/WixSharp/WixProject.cs
index dd5fd887..6a26d66b 100644
--- a/Source/src/WixSharp/WixProject.cs
+++ b/Source/src/WixSharp/WixProject.cs
@@ -164,11 +164,6 @@ public string Language
         /// </summary>
         public string CandleOptions = "";
 
-        /// <summary>
-        /// WiX compiler <c>wix.exe</c> options (e.g. "-define DEBUG"). Available only in WiX v4.*
-        /// </summary>
-        public string WixOptions = "";
-
         /// <summary>
         /// Occurs when WiX source code generated. Use this event if you need to modify generated XML (XDocument)
         /// before it is compiled into MSI.
diff --git a/Source/src/WixSharp/WixSharp.csproj b/Source/src/WixSharp/WixSharp.csproj
index a16aa6a2..1632e36b 100644
--- a/Source/src/WixSharp/WixSharp.csproj
+++ b/Source/src/WixSharp/WixSharp.csproj
@@ -281,11 +281,6 @@
       <Name>WixSharp.Msi</Name>
     </ProjectReference>
   </ItemGroup>
-  <ItemGroup>
-    <PackageReference Include="WixToolset.Dtf.WindowsInstaller">
-      <Version>4.0.0</Version>
-    </PackageReference>
-  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.