diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
index af59714..d65cd18 100644
--- a/.github/workflows/build-and-test.yml
+++ b/.github/workflows/build-and-test.yml
@@ -11,6 +11,7 @@ on:
       - main
     paths:
       - src/**
+  workflow_dispatch:
 
 jobs:
   build:
@@ -25,7 +26,6 @@ jobs:
       with:
         dotnet-version: |
             9.x
-            6.x
 
     - name: Restore dependencies
       run: dotnet restore src/WeakEvent.sln
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index eabbb78..66ec0db 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -11,6 +11,7 @@ on:
       - src/**
   schedule:
     - cron: '20 6 * * 5'
+  workflow_dispatch:
 
 jobs:
   analyze:
@@ -36,7 +37,6 @@ jobs:
         with:
           dotnet-version: |
             9.x
-            6.x
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v3
diff --git a/.github/workflows/publish-nuget.yml b/.github/workflows/publish-nuget.yml
index 7a73c23..290779f 100644
--- a/.github/workflows/publish-nuget.yml
+++ b/.github/workflows/publish-nuget.yml
@@ -18,7 +18,6 @@ jobs:
       with:
         dotnet-version: |
             9.x
-            6.x
 
     - name: 'Get Version'
       id: version
diff --git a/README.md b/README.md
index c62b150..5f3cda8 100644
--- a/README.md
+++ b/README.md
@@ -20,8 +20,7 @@ In the context of Blazor components, this functionality is particularly valuable
 
 ## Features
 
-![.NET 9.0](https://img.shields.io/badge/.NET-9.0-brightgreen)
-![.NET 6.0](https://img.shields.io/badge/.NET-6.0-brightgreen)
+![.NET Standard 2.0](https://img.shields.io/badge/.NET_Standard-2.0-brightgreen)
 
 - **Weak References:** Subscribers are held via weak references, allowing the garbage collector to reclaim them when they are no longer needed.
 - **Events With or Without Data:** Use `WeakEvent<TEvent>` when you need to pass event data to subscribers, or `WeakEvent` for simple notifications that don't require additional information.
diff --git a/src/WeakEvent.Tests/WeakEvent.Tests.csproj b/src/WeakEvent.Tests/WeakEvent.Tests.csproj
index c85678b..d890460 100644
--- a/src/WeakEvent.Tests/WeakEvent.Tests.csproj
+++ b/src/WeakEvent.Tests/WeakEvent.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net9.0;net6.0</TargetFrameworks>
+    <TargetFramework>net9.0</TargetFramework>
 	<LangVersion>latest</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
diff --git a/src/WeakEvent/WeakEvent.cs b/src/WeakEvent/WeakEvent.cs
index 27e2d6a..156f484 100644
--- a/src/WeakEvent/WeakEvent.cs
+++ b/src/WeakEvent/WeakEvent.cs
@@ -160,7 +160,10 @@ public abstract class WeakEventBase
 	/// <exception cref="ArgumentNullException">Thrown when <paramref name="handler"/> is null.</exception>
 	protected void Subscribe(Delegate handler)
 	{
-		ArgumentNullException.ThrowIfNull(handler);
+		if (handler is null)
+		{
+			throw new ArgumentNullException(nameof(handler));
+		}
 
 		_handlers.Add(new WeakEventHandler(handler));
 	}
@@ -172,7 +175,10 @@ protected void Subscribe(Delegate handler)
 	/// <exception cref="ArgumentNullException">Thrown when <paramref name="handler"/> is null.</exception>
 	protected bool Unsubscribe(Delegate handler)
 	{
-		ArgumentNullException.ThrowIfNull(handler);
+		if (handler is null)
+		{
+			throw new ArgumentNullException(nameof(handler));
+		}
 
 		return _handlers.RemoveAll(weh => weh.Matches(handler)) > 0;
 	}
diff --git a/src/WeakEvent/WeakEvent.csproj b/src/WeakEvent/WeakEvent.csproj
index 4b95873..da993fc 100644
--- a/src/WeakEvent/WeakEvent.csproj
+++ b/src/WeakEvent/WeakEvent.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>net9.0;net6.0</TargetFrameworks>
+    <TargetFramework>netstandard2.0</TargetFramework>
     <LangVersion>latest</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>