Expose AppContext.SetData in ref assembly (dotnet#62996)

* Expose AppContext.SetData in ref assembly

* Implement test for Set/GetData

* Add doc comment

src/libraries/System.Private.CoreLib/src/System/AppContext.cs

@@ -45,6 +45,12 @@ public static partial class AppContext
             return data;
         }
 
+        /// <summary>
+        /// Sets the value of the named data element assigned to the current application domain.
+        /// </summary>
+        /// <param name="name">The name of the data element</param>
+        /// <param name="data">The value of <paramref name="name"/></param>
+        /// <exception cref="ArgumentNullException">If <paramref name="name"/> is <see langword="null"/></exception>
         public static void SetData(string name, object? data)
         {
             if (name == null)

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -112,6 +112,7 @@ public static partial class AppContext
         public static string BaseDirectory { get { throw null; } }
         public static string? TargetFrameworkName { get { throw null; } }
         public static object? GetData(string name) { throw null; }
+        public static void SetData(string name, object? data) { }
         public static void SetSwitch(string switchName, bool isEnabled) { }
         public static bool TryGetSwitch(string switchName, out bool isEnabled) { throw null; }
     }

src/libraries/System.Runtime/tests/System.Runtime.Tests.csproj

@@ -144,8 +144,9 @@
     <Compile Include="System\ValueTypeTests.cs" />
     <Compile Include="System\VersionTests.cs" />
     <Compile Include="System\WeakReferenceTests.cs" />
-    <Compile Include="System\AppContext\AppContext.Switch.cs" />
-    <Compile Include="System\AppContext\AppContext.Switch.Validation.cs" />
+    <Compile Include="System\AppContext\AppContextTests.cs" />
+    <Compile Include="System\AppContext\AppContextTests.Switch.cs" />
+    <Compile Include="System\AppContext\AppContextTests.Switch.Validation.cs" />
     <Compile Include="System\Collections\Generic\KeyNotFoundExceptionTests.cs" />
     <Compile Include="System\Collections\Generic\KeyValuePairTests.cs" />
     <Compile Include="System\Collections\ObjectModel\CollectionTests.cs" />

src/libraries/System.Runtime/tests/System/AppContext/AppContextTests.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+namespace System.Tests
+{
+    public partial class AppContextTests
+    {
+        [Theory]
+        [InlineData("AppContext_Case1", 123)]
+        [InlineData("AppContext_Case2", "")]
+        [InlineData("AppContext_Case3", null)]
+        public void AppContext_GetSetDataTest(string dataKey, object value)
+        {
+            // Set data
+            AppContext.SetData(dataKey, value);
+
+            // Get previously set data
+            object actual = AppContext.GetData(dataKey);
+
+            // Validate instance equality
+            Assert.Same(value, actual);
+        }
+
+        [Fact]
+        public void AppContext_ThrowTest()
+        {
+            AssertExtensions.Throws<ArgumentNullException>("name", () => AppContext.SetData(null, 123));
+        }
+    }
+}