React to removal of PlatformAbstractions (#257)

- Part of aspnet/PlatformAbstractions#50

src/Benchmarks/Middleware/DebugInfoPageMiddleware.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved. 
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information. 
 
+using System;
 using System.Linq;
 using System.Runtime;
 using System.Threading.Tasks;
@@ -10,7 +11,6 @@
 using Microsoft.AspNetCore.Hosting.Server.Features;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;
-using Microsoft.Extensions.PlatformAbstractions;
 
 namespace Benchmarks.Middleware
 {
@@ -24,6 +24,14 @@ public class DebugInfoPageMiddleware
         private static readonly string _configurationName = "";
 #endif
 
+#if NET46
+        private static readonly string _targetFrameworkName = AppDomain.CurrentDomain.SetupInformation.TargetFrameworkName;
+#elif NETCOREAPP2_0
+        private static readonly string _targetFrameworkName = AppContext.TargetFrameworkName;
+#else
+#error the target framework needs to be updated.                    
+#endif
+
         private readonly IHostingEnvironment _hostingEnv;
         private readonly RequestDelegate _next;
         private readonly Scenarios _scenarios;
@@ -46,7 +54,7 @@ public async Task Invoke(HttpContext httpContext)
             await httpContext.Response.WriteAsync("<h2>Configuration Information</h2>");
             await httpContext.Response.WriteAsync("<ul>");
             await httpContext.Response.WriteAsync($"<li>Environment: {_hostingEnv.EnvironmentName}</li>");
-            await httpContext.Response.WriteAsync($"<li>Framework: {PlatformServices.Default.Application.RuntimeFramework.FullName}</li>");
+            await httpContext.Response.WriteAsync($"<li>Framework: {_targetFrameworkName}</li>");
             await httpContext.Response.WriteAsync($"<li>Server GC enabled: {GCSettings.IsServerGC}</li>");
             await httpContext.Response.WriteAsync($"<li>Configuration: {_configurationName}</li>");
             await httpContext.Response.WriteAsync($"<li>Server: {Program.Server}</li>");