Switch to WebClient sync api

We were using `HttpClient` and calling `.Result` on one of the async methods that uses it which can result in a deadlock and might have been causing random locking in the VS IDE.  This switches to using `HttpWebRequest` and all synchronous API's to avoid this possible deadlock.  We also control the request timeout and set it to a lower 10 seconds as it's not a critical request we don't want to block the IDE too long.

Author: Redth

source/buildtasks/support-annotations/NugetPackages.cs

@@ -2,7 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using System.Net.Http;
+using System.Net;
 using System.Runtime.Serialization.Json;
 using System.Runtime.Versioning;
 using System.Text.RegularExpressions;
@@ -16,6 +16,8 @@ namespace Xamarin.Android.Support.BuildTasks
 {
 	public static class NugetPackages
 	{
+		const int WEB_REQUEST_TIMEOUT_MS = 10000;
+
 		public static readonly Dictionary<int, Version> AndroidApiLevelsAndVersions = new Dictionary<int, Version>
 		{
 			{ 23, new Version(6, 0) },
@@ -127,20 +129,18 @@ public static string GetSupportVersion(string packageIdPrefix, Dictionary<string
 			return supportVersion;
 		}
 
-		static readonly HttpClient http = new HttpClient();
-
-		public static async Task<string> GetRecommendedSupportPackageVersion(int apiLevel)
+		public static string GetRecommendedSupportPackageVersion(int apiLevel)
 		{
 			// Default to the apilevel.x since this is displayed as a suggestion in a message
 			var bestVersion = apiLevel.ToString() + ".x";
 
 			try
 			{
-				var searchUrl = await GetNuGetSearchUrl();
+				var searchUrl = GetNuGetSearchUrl();
 
 				var queryUrl = searchUrl + "?q=packageid:Xamarin.Android.Support.Annotations&prerelease=false";
 
-				var data = await http.GetStringAsync(queryUrl);
+				var data = DownloadString(queryUrl);
 
 				var js = new JavaScriptSerializer();
 				var json = js.Deserialize<dynamic>(data);
@@ -161,9 +161,9 @@ public static async Task<string> GetRecommendedSupportPackageVersion(int apiLeve
 			return bestVersion;
 		}
 
-		static async Task<string> GetNuGetSearchUrl()
+		static string GetNuGetSearchUrl()
 		{
-			var data = await http.GetStringAsync("https://api.nuget.org/v3/index.json");
+			var data = DownloadString("https://api.nuget.org/v3/index.json");
 
 			var js = new JavaScriptSerializer();
 			var json = js.Deserialize<dynamic>(data);
@@ -175,5 +175,22 @@ static async Task<string> GetNuGetSearchUrl()
 
 			return null;
 		}
+
+		static string DownloadString(string url)
+		{
+			var result = string.Empty;
+
+			var request = (HttpWebRequest)WebRequest.Create(url);
+			request.Timeout = WEB_REQUEST_TIMEOUT_MS;
+			request.ReadWriteTimeout = WEB_REQUEST_TIMEOUT_MS;
+
+			using (var response = (HttpWebResponse)request.GetResponse())
+			using (var respStream = response.GetResponseStream())
+			using (var sr = new StreamReader(respStream)) {
+				result = sr.ReadToEnd();
+			}
+
+			return result;
+		}
 	}
 }

source/buildtasks/support-annotations/Support-Annotations-BuildTasks.csproj

@@ -40,9 +40,6 @@
     <Reference Include="System.Runtime.Serialization" />
     <Reference Include="System.Web.Extensions" />
     <Reference Include="Microsoft.CSharp" />
-    <Reference Include="System.Net.Http">
-      <HintPath>..\..\..\..\..\..\Library\Frameworks\Mono.framework\Versions\5.16.0\lib\mono\xbuild\Microsoft\Microsoft.NET.Build.Extensions\net461\lib\System.Net.Http.dll</HintPath>
-    </Reference>
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Properties\AssemblyInfo.cs" />

source/buildtasks/support-annotations/VerifyVersionsTask.cs

@@ -83,7 +83,7 @@ public override bool Execute()
 				sb.AppendLine("The following Xamarin.Android.Support.* packages and versions were detected:");
 				sb.AppendLine();
 
-				var recommendedSupportVersion = NugetPackages.GetRecommendedSupportPackageVersion(apiLevel).Result;
+				var recommendedSupportVersion = NugetPackages.GetRecommendedSupportPackageVersion(apiLevel);
 
 				foreach (var pkg in packageVersions)
 					sb.AppendLine($"    {pkg.Key} ({pkg.Value})");