refactor: Allow ManualTimeProvider.Start to be set using property initializers

Author: egil

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Added `ActiveTimers` property to `ManualTimeProvider`. The property will display the number of currently active timers that have a callback scheduled to be called in the future.
 
+- Allow `ManualTimeProvider.Start` to be set using property initializers.
+
 ## [1.0.0-rc.1]
 
 - Updated Microsoft.Bcl.TimeProvider package dependency to rc.1 version.

docs/TimeProviderExtensions.ManualTimeProvider.md

@@ -135,7 +135,7 @@ The default implementation returns [System.TimeZoneInfo.Local](https://docs.micr
 Gets the starting date and time for this provider.
 
 ```csharp
-public System.DateTimeOffset Start { get; }
+public System.DateTimeOffset Start { get; set; }
 ```
 
 #### Property Value

src/TimeProviderExtensions/ManualTimeProvider.cs

@@ -29,7 +29,7 @@ public partial class ManualTimeProvider : TimeProvider
     /// <summary>
     /// Gets the starting date and time for this provider.
     /// </summary>
-    public DateTimeOffset Start { get; }
+    public DateTimeOffset Start { get; init; }
 
     /// <summary>
     /// Gets or sets the amount of time by which time advances whenever the clock is read via <see cref="GetUtcNow"/>.

src/TimeProviderExtensions/System.Runtime.CompilerServices/IsExternalInit.cs

@@ -0,0 +1,19 @@
+#if NETSTANDARD2_0
+// 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.
+    /// This dummy class is required to compile records when targeting .NET Standard
+    /// </summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    internal static class IsExternalInit
+    {
+    }
+}
+#endif