Fix #1720: Support new path structure of reference assemblies with .NET Core 3.0

ILSpy.AddIn/AssemblyFileFinder.cs

@@ -38,7 +38,7 @@ namespace ICSharpCode.ILSpy.AddIn
 
 		static readonly string DetectTargetFrameworkIdRefPathPattern =
 			@"(Reference Assemblies[/\\]Microsoft[/\\]Framework[/\\](?<1>.NETFramework)[/\\]v(?<2>[^/\\]+)[/\\])" +
-			@"|(NuGetFallbackFolder[/\\](?<1>[^/\\]+)\\(?<2>[^/\\]+)([/\\].*)?[/\\]ref[/\\])";
+			@"|((NuGetFallbackFolder|packs)[/\\](?<1>[^/\\]+)\\(?<2>[^/\\]+)([/\\].*)?[/\\]ref[/\\])";
 
 		public static string DetectTargetFrameworkId(AssemblyDefinition assembly, string assemblyPath = null)
 		{
@@ -63,6 +63,7 @@ namespace ICSharpCode.ILSpy.AddIn
 				 * 
 				 * - .NETFramework -> C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\mscorlib.dll
 				 * - .NETCore      -> C:\Program Files\dotnet\sdk\NuGetFallbackFolder\microsoft.netcore.app\2.1.0\ref\netcoreapp2.1\System.Console.dll
+				 *                 -> C:\Program Files\dotnet\packs\Microsoft.NETCore.App.Ref\3.0.0\ref\netcoreapp3.0\System.Runtime.Extensions.dll
 				 * - .NETStandard  -> C:\Program Files\dotnet\sdk\NuGetFallbackFolder\netstandard.library\2.0.3\build\netstandard2.0\ref\netstandard.dll
 				 */
 				var pathMatch = Regex.Match(assemblyPath, DetectTargetFrameworkIdRefPathPattern,
@@ -73,9 +74,9 @@ namespace ICSharpCode.ILSpy.AddIn
 
 					if (type == ".NETFramework") {
 						return $".NETFramework,Version=v{version}";
-					} else if (type.Contains("netcore")) {
+					} else if (type.ToLower().Contains("netcore")) {
 						return $".NETCoreApp,Version=v{version}";
-					} else if (type.Contains("netstandard")) {
+					} else if (type.ToLower().Contains("netstandard")) {
 						return $".NETStandard,Version=v{version}";
 					}
 				}