fix(build): Resolve MultiTarget framework build errors

Author: arttonoyan

OpenFeature.sln

@@ -83,7 +83,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenFeature.DependencyInjec
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenFeature.DependencyInjection.Tests", "test\OpenFeature.DependencyInjection.Tests\OpenFeature.DependencyInjection.Tests.csproj", "{EB35F9F6-8A79-410E-A293-9387BC4AC9A7}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "OpenFeature.Hosting", "src\OpenFeature.Hosting\OpenFeature.Hosting.csproj", "{C99DA02A-3981-45A6-B3F8-4A1A48653DEE}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenFeature.Hosting", "src\OpenFeature.Hosting\OpenFeature.Hosting.csproj", "{C99DA02A-3981-45A6-B3F8-4A1A48653DEE}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

src/OpenFeature.DependencyInjection/MultiTarget/CallerArgumentExpressionAttribute.cs

@@ -0,0 +1,23 @@
+// @formatter:off
+// ReSharper disable All
+#if NETCOREAPP3_0_OR_GREATER
+// https://github.com/dotnet/runtime/issues/96197
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.CallerArgumentExpressionAttribute))]
+#else
+#pragma warning disable
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Runtime.CompilerServices;
+
+[AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
+internal sealed class CallerArgumentExpressionAttribute : Attribute
+{
+    public CallerArgumentExpressionAttribute(string parameterName)
+    {
+        ParameterName = parameterName;
+    }
+
+    public string ParameterName { get; }
+}
+#endif

src/OpenFeature.DependencyInjection/MultiTarget/Guard.cs

@@ -0,0 +1,20 @@
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace OpenFeature;
+
+[DebuggerStepThrough]
+internal static class Guard
+{
+    public static T ThrowIfNull<T>(T? value, [CallerArgumentExpression("value")] string name = null!)
+    {
+#if NET8_0_OR_GREATER
+        ArgumentNullException.ThrowIfNull(value, name);
+#else
+        if (value is null)
+            throw new ArgumentNullException(name);
+#endif
+
+        return value;
+    }
+}

src/OpenFeature.DependencyInjection/MultiTarget/IsExternalInit.cs

@@ -0,0 +1,21 @@
+// @formatter:off
+// ReSharper disable All
+#if NET5_0_OR_GREATER
+// https://github.com/dotnet/runtime/issues/96197
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.IsExternalInit))]
+#else
+#pragma warning disable
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices;
+
+/// <summary>
+/// Reserved to be used by the compiler for tracking metadata.
+/// This class should not be used by developers in source code.
+/// </summary>
+[EditorBrowsable(EditorBrowsableState.Never)]
+static class IsExternalInit { }
+#endif

src/OpenFeature.DependencyInjection/OpenFeature.DependencyInjection.csproj

@@ -1,7 +1,7 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net6.0;net8.0;net462</TargetFrameworks>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <RootNamespace>OpenFeature</RootNamespace>
@@ -24,4 +24,8 @@
     </AssemblyAttribute>
   </ItemGroup>
 
+  <ItemGroup>
+    <Folder Include="MultiTarget\" />
+  </ItemGroup>
+
 </Project>

src/OpenFeature.DependencyInjection/OpenFeatureBuilder.cs

@@ -5,7 +5,7 @@ namespace OpenFeature;
 /// <summary>
 /// Describes a <see cref="OpenFeatureBuilder"/> backed by an <see cref="IServiceCollection"/>.
 /// </summary>
-/// <param name="Services"><see cref="IServiceCollection"/></param>
+/// <param name="Services">The <see cref="IServiceCollection"/> instance.</param>
 public sealed record OpenFeatureBuilder(IServiceCollection Services)
 {
     /// <summary>

src/OpenFeature.DependencyInjection/OpenFeatureBuilderExtensions.cs

@@ -18,8 +18,8 @@ public static OpenFeatureBuilder AddContext(
         this OpenFeatureBuilder builder,
         Action<EvaluationContextBuilder> configure)
     {
-        ArgumentNullException.ThrowIfNull(builder);
-        ArgumentNullException.ThrowIfNull(configure);
+        Guard.ThrowIfNull(builder);
+        Guard.ThrowIfNull(configure);
 
         return builder.AddContext((b, _) => configure(b));
     }
@@ -34,8 +34,8 @@ public static OpenFeatureBuilder AddContext(
         this OpenFeatureBuilder builder,
         Action<EvaluationContextBuilder, IServiceProvider> configure)
     {
-        ArgumentNullException.ThrowIfNull(builder);
-        ArgumentNullException.ThrowIfNull(configure);
+        Guard.ThrowIfNull(builder);
+        Guard.ThrowIfNull(configure);
 
         builder.IsContextConfigured = true;
         builder.Services.TryAddTransient(provider =>
@@ -58,7 +58,7 @@ public static OpenFeatureBuilder AddContext(
     public static OpenFeatureBuilder AddProvider<T>(this OpenFeatureBuilder builder, Func<IServiceProvider, T> providerFactory)
         where T : FeatureProvider
     {
-        ArgumentNullException.ThrowIfNull(builder);
+        Guard.ThrowIfNull(builder);
         builder.Services.TryAddSingleton<FeatureProvider>(providerFactory);
         return builder;
     }

src/OpenFeature.DependencyInjection/OpenFeatureServiceCollectionExtensions.cs

@@ -19,8 +19,8 @@ public static class OpenFeatureServiceCollectionExtensions
     /// <returns>the current <see cref="IServiceCollection"/> instance</returns>
     public static IServiceCollection AddOpenFeature(this IServiceCollection services, Action<OpenFeatureBuilder> configure)
     {
-        ArgumentNullException.ThrowIfNull(services);
-        ArgumentNullException.ThrowIfNull(configure);
+        Guard.ThrowIfNull(services);
+        Guard.ThrowIfNull(configure);
 
         services.TryAddSingleton(Api.Instance);
         services.TryAddSingleton<IFeatureLifecycleManager, FeatureLifecycleManager>();