Enable binding ApiVersion in Minimal APIs

Author: commonsensesoftware

src/AspNetCore/WebApi/src/Asp.Versioning.Http/DependencyInjection/IServiceCollectionExtensions.cs

@@ -17,7 +17,7 @@ namespace Microsoft.Extensions.DependencyInjection;
 /// Provides extension methods for the <see cref="IServiceCollection"/> interface.
 /// </summary>
 [CLSCompliant( false )]
-public static class IServiceCollectionExtensions
+public static partial class IServiceCollectionExtensions
 {
     /// <summary>
     /// Adds service API versioning to the specified services collection.

src/AspNetCore/WebApi/src/Asp.Versioning.Http/net6.0/DependencyInjection/IServiceCollectionExtensions.cs

@@ -0,0 +1,47 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+
+namespace Microsoft.Extensions.DependencyInjection;
+
+using Asp.Versioning;
+using Microsoft.AspNetCore.Http;
+
+/// <content>
+/// Provides additional implementation specific to .NET 6.0.
+/// </content>
+public static partial class IServiceCollectionExtensions
+{
+    /// <summary>
+    /// Enables binding the <see cref="ApiVersion"/> type in Minimal API parameters..
+    /// </summary>
+    /// <param name="builder">The extended <see cref="IApiVersioningBuilder">API versioning builder</see>.</param>
+    /// <returns>The original <paramref name="builder"/>.</returns>
+    public static IApiVersioningBuilder EnableApiVersionBinding( this IApiVersioningBuilder builder )
+    {
+        if ( builder == null )
+        {
+            throw new ArgumentNullException( nameof( builder ) );
+        }
+
+        // currently required because there is no other hook.
+        // 1. TryParse does not work because:
+        //    a. Parsing is delegated to IApiVersionParser.TryParse
+        //    b. The result can come from multiple locations
+        //    c. There can be multiple results
+        // 2. BindAsync does not work because:
+        //    a. It is static and must be on the ApiVersion type
+        //    b. It is specific to ASP.NET Core
+        builder.Services.AddHttpContextAccessor();
+
+        // this registration is 'truthy'. it is possible for the requested API version to be null; however, but the time this is
+        // resolved for a request delegate it can only be null if the API is version-neutral and no API version was requested. this
+        // should be a rare and nonsensical scenario. declaring the parameter as ApiVersion? should be expect and solve the issue
+        //
+        // it should also be noted that this registration allows resolving the requested API version from virtually any context.
+        // that is not intended, which is why this extension is not named something more general such as AddApiVersionAsService.
+        // if/when a better parameter binding mechanism becomes available, this method is expected to become obsolete, no-op, and
+        // eventually go away.
+        builder.Services.AddTransient( sp => sp.GetRequiredService<IHttpContextAccessor>().HttpContext?.GetRequestedApiVersion()! );
+
+        return builder;
+    }
+}