2012-07-07 Proxy Objects post: http://www.ipreferjim.com/2012/07/prox…

…y-objects/

2012-07-07/Proxies/AssemblyInfo.cs

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+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+// Information about this assembly is defined by the following attributes. 
+// Change them to the values specific to your project.
+
+[assembly: AssemblyTitle("Proxies")]
+[assembly: AssemblyDescription("")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("")]
+[assembly: AssemblyProduct("")]
+[assembly: AssemblyCopyright("jim")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+// The assembly version has the format "{Major}.{Minor}.{Build}.{Revision}".
+// The form "{Major}.{Minor}.*" will automatically update the build and revision,
+// and "{Major}.{Minor}.{Build}.*" will update just the revision.
+
+[assembly: AssemblyVersion("1.0.*")]
+
+// The following attributes are used to specify the signing key for the assembly, 
+// if desired. See the Mono documentation for more information about signing.
+
+//[assembly: AssemblyDelaySign(false)]
+//[assembly: AssemblyKeyFile("")]
+

2012-07-07/Proxies/Foo.cs

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+using System;
+using System.IO;
+
+namespace Proxies
+{
+	public interface IFoo: ILogger {
+		ILogger Logger {get;set;}
+		string ShowBar();
+	}
+
+	/// <summary>
+	/// Foo. This class represents a simple proxy object using DI.
+	/// <remarks>Requries ILogger instance</remarks>
+	/// </summary>
+	public class Foo : IFoo
+	{
+		public ILogger Logger {
+			get;
+			set;
+		}
+
+		public Foo() { }
+		public Foo (ILogger logger)
+		{
+			Logger = logger;
+		}
+
+		public virtual void Write(string msg) {
+			Logger.Write(msg);
+		}
+
+		public string ShowBar() {
+			return "Bar";
+		}
+
+		public string ShowBaz() {
+			return "Baz";
+		}
+	}
+}
+

2012-07-07/Proxies/FooClassProxy.cs

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+using System;
+
+namespace Proxies
+{
+	public class FooClassProxy : Foo
+	{
+		public FooClassProxy (ILogger logger) : base(logger)
+		{
+		}
+
+		public override void Write (string msg)
+		{
+			base.Write (String.Format("Message: {0}\n", msg));
+		}
+	}
+}
+

2012-07-07/Proxies/FooInterfaceProxy.cs

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+using System;
+using System.IO;
+
+namespace Proxies
+{
+	/// <summary>
+	/// Concrete foo proxy. This is interface-based proxying. 
+	/// i.e. FooInterfaceProxy "is a" Foo and proxies Foo.Write by overriding the virtual method Write.
+	/// </summary>
+	public class FooInterfaceProxy : IFoo {
+		private IFoo _foo;
+
+		public ILogger Logger {
+			get;
+			set;
+		}
+
+		public FooInterfaceProxy(ILogger logger)
+		{
+			Logger = logger;
+		}
+
+		public void Write (string msg)
+		{
+			Logger.Write("Trace: FooInterfaceProxy.Write enter.");
+			if(_foo == null) {
+				Logger.Write("Trace: Creating new Foo");
+				_foo = new Foo(Logger);
+			}
+			_foo.Write(msg);
+			Logger.Write("Trace: FooInterfaceProxy.Write exit.\n");
+		}
+
+		public string ShowBar() {
+			if(_foo == null) {
+				throw new InvalidOperationException("FooBar :(");
+			}
+			return _foo.ShowBar();
+		}
+	}
+}

2012-07-07/Proxies/Logger.cs

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+using System;
+using System.IO;
+
+namespace Proxies
+{
+	public interface ILogger {
+		void Write(string msg);
+	}
+
+	/// <summary>
+	/// Logger. This class represents a simple wrapper object.
+	/// <para>
+	/// Logger proxies calls to TextWriter.WriteLine via the Write method, 
+	/// but Logger is technically *not* a proxy object because it is not a TextWriter.
+	/// </para>		
+	/// <remarks>Requires a TextWriter instance to write to</remarks>
+	/// </summary>
+	public class Logger : ILogger
+	{
+		public TextWriter Writer {
+			get;
+			set;
+		}
+
+		public Logger(TextWriter writer) {
+			Writer = writer;
+		}
+
+		public virtual void Write(string msg) {
+			Writer.WriteLine(msg);
+		}
+	}
+}

2012-07-07/Proxies/Main.cs

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+using System;
+using Castle.DynamicProxy;
+using System.Diagnostics;
+
+namespace Proxies
+{
+	class MainClass
+	{
+		public static void Main (string[] args)
+		{
+			// Add Console.Out as a listener for Debug.WriteLine to show in Mono
+			Debug.Listeners.Add( new ConsoleTraceListener(useErrorStream: false) );
+
+			// Using dependency injection to specify output stream
+			// i.e. Foo proxies ILogger
+			ILogger logger = new Logger (Console.Out);
+			Foo foo = new Foo (logger);
+			foo.Write ("Testing Foo\n");
+
+			Console.WriteLine("Hard-coded proxy object demonstrating trace logging:");
+			// You could create a second foo type which appears to be IFoo
+			// but actually traces method enter/exit by proxy
+			IFoo foo2 = new FooInterfaceProxy (logger);
+			foo2.Write ("Testing FooInterfaceProxy #1");
+			foo2.Write ("Testing FooInterfaceProxy #2");
+
+			Console.WriteLine("Hard-coded proxy object demonstrating added functionality:");
+			IFoo foo3 = new FooClassProxy(logger);
+			foo3.Write("Testing FooClassProxy");
+
+			Console.WriteLine("Dynamically proxy an existing object's virtual members (any object works):");
+			var proxify = new ProxyGenerator();
+			var interceptors = new IInterceptor[] { new DebugLogger() };
+			Foo foo4 = proxify.CreateClassProxyWithTarget(foo, interceptors);
+			foo4.Write("Class Foo proxied dynamically using CreateClassProxyWithTarget");
+			Console.WriteLine("Calling Class Foo's ToString(): {0}", foo4.ToString());
+			Console.WriteLine("Calling IFoo.ShowBar(): {0}", foo4.ShowBar());
+			Console.WriteLine("Calling Foo.ShowBaz(): {0}\n", foo4.ShowBaz());
+
+			Console.WriteLine ("Dynamic Proxy a specific target:");
+			IFoo foo5 = (IFoo)proxify.CreateInterfaceProxyWithTarget(typeof(IFoo), foo, interceptors);
+			foo5.Write("Class Foo proxied dynamically using CreateInterfaceProxyWithTarget");
+			Console.WriteLine("Calling Class Foo's ToString(): {0}\n", foo5.ToString());
+			Console.WriteLine("Calling IFoo.ShowBar(): {0}", foo5.ShowBar());
+			Console.WriteLine("Notice the order of interception above.");
+		}
+
+		public class DebugLogger : IInterceptor
+		{
+			#region IInterceptor implementation
+			public void Intercept (IInvocation invocation)
+			{
+				Debug.WriteLine("Debug: proxy enter.");
+				invocation.Proceed();
+				Debug.WriteLine("Debug: proxy exit.");
+			}
+			#endregion
+		}
+	}
+}

2012-07-07/Proxies/Proxies.csproj

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+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">x86</Platform>
+    <ProductVersion>10.0.0</ProductVersion>
+    <SchemaVersion>2.0</SchemaVersion>
+    <ProjectGuid>{3F63B14B-482E-44AC-B045-DDD710EAE270}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <RootNamespace>Proxies</RootNamespace>
+    <AssemblyName>Proxies</AssemblyName>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|x86' ">
+    <DebugSymbols>True</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>False</Optimize>
+    <OutputPath>bin\Debug</OutputPath>
+    <DefineConstants>DEBUG;</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+    <PlatformTarget>x86</PlatformTarget>
+    <Externalconsole>True</Externalconsole>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|x86' ">
+    <DebugType>none</DebugType>
+    <Optimize>True</Optimize>
+    <OutputPath>bin\Release</OutputPath>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+    <PlatformTarget>x86</PlatformTarget>
+    <Externalconsole>True</Externalconsole>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="Castle.Core">
+      <HintPath>..\..\deps\Castle3.0\Castle.Core.dll</HintPath>
+    </Reference>
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="Main.cs" />
+    <Compile Include="AssemblyInfo.cs" />
+    <Compile Include="Foo.cs" />
+    <Compile Include="Logger.cs" />
+    <Compile Include="FooInterfaceProxy.cs" />
+    <Compile Include="FooClassProxy.cs" />
+  </ItemGroup>
+  <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
+</Project>

2012-07-07/Proxies/Proxies.sln

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+
+Microsoft Visual Studio Solution File, Format Version 11.00
+# Visual Studio 2010
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Proxies", "Proxies.csproj", "{3F63B14B-482E-44AC-B045-DDD710EAE270}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|x86 = Debug|x86
+		Release|x86 = Release|x86
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{3F63B14B-482E-44AC-B045-DDD710EAE270}.Debug|x86.ActiveCfg = Debug|x86
+		{3F63B14B-482E-44AC-B045-DDD710EAE270}.Debug|x86.Build.0 = Debug|x86
+		{3F63B14B-482E-44AC-B045-DDD710EAE270}.Release|x86.ActiveCfg = Release|x86
+		{3F63B14B-482E-44AC-B045-DDD710EAE270}.Release|x86.Build.0 = Release|x86
+	EndGlobalSection
+	GlobalSection(MonoDevelopProperties) = preSolution
+		StartupItem = Proxies.csproj
+	EndGlobalSection
+EndGlobal