AOT and x-plat changes (#3203)

* Make AboutPage AOT-friendlier
* Fix AOT and x-plat settings path inference

ILSpy/AboutPage.cs

@@ -54,7 +54,7 @@ namespace ICSharpCode.ILSpy
 			};
 			output.WriteLine(Resources.ILSpyVersion + DecompilerVersionInfo.FullVersion);
 
-			string prodVersion = System.Diagnostics.FileVersionInfo.GetVersionInfo(typeof(Uri).Assembly.Location).ProductVersion;
+			string prodVersion = GetDotnetProductVersion();
 			output.WriteLine(Resources.NETFrameworkVersion + prodVersion);
 
 			output.AddUIElement(
@@ -104,6 +104,27 @@ namespace ICSharpCode.ILSpy
 			textView.ShowText(output);
 		}
 
+		private static string GetDotnetProductVersion()
+		{
+			// In case of AOT .Location is null, we need a fallback for that
+			string assemblyLocation = typeof(Uri).Assembly.Location;
+
+			if (!String.IsNullOrWhiteSpace(assemblyLocation))
+			{
+				return System.Diagnostics.FileVersionInfo.GetVersionInfo(assemblyLocation).ProductVersion;
+			}
+			else
+			{
+				var version = typeof(Object).Assembly.GetName().Version;
+				if (version != null)
+				{
+					return version.ToString();
+				}
+			}
+
+			return "UNKNOWN";
+		}
+
 		sealed class MyLinkElementGenerator : LinkElementGenerator
 		{
 			readonly Uri uri;

ILSpy/ILSpySettingsFilePathProvider.cs

@@ -29,10 +29,16 @@ namespace ICSharpCode.ILSpy
 		{
 			if (App.CommandLineArguments.ConfigFile != null)
 				return App.CommandLineArguments.ConfigFile;
-			string localPath = Path.Combine(Path.GetDirectoryName(typeof(MainWindow).Assembly.Location), "ILSpy.xml");
+
+			var assemblyLocation = typeof(MainWindow).Assembly.Location;
+			if (!String.IsNullOrWhiteSpace(assemblyLocation))
+			{
+				string localPath = Path.Combine(Path.GetDirectoryName(assemblyLocation), "ILSpy.xml");
 				if (File.Exists(localPath))
 					return localPath;
-			return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "ICSharpCode\\ILSpy.xml");
+			}
+
+			return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "ICSharpCode", "ILSpy.xml");
 		}
 	}
 }