Improve error message when running on systems with required libraries missing

Programs/GridProxyGUI/Program.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using Gtk;
 
 namespace GridProxyGUI
@@ -7,10 +8,64 @@ namespace GridProxyGUI
     {
         public static void Main(string[] args)
         {
-            Application.Init();
-            MainWindow win = new MainWindow();
-            win.Show();
-            Application.Run();
+            try
+            {
+                StartGtkApp();
+            }
+            catch (Exception ex)
+            {
+                if (ex is TypeInitializationException || ex is TypeLoadException || ex is System.IO.FileNotFoundException)
+                {
+                    NativeApi.ExitWithMessage("Failed to start", ex.Message + "\n\nMake sure tha application install isn't missing accompanied files and that Gtk# is installed.", 1);
+                }
+                throw;
+            }
+        }
+
+        static void StartGtkApp()
+        {
+                Gtk.Application.Init();
+                MainWindow win = new MainWindow();
+                win.Show();
+                Application.Run();
+        }
+    }
+
+    public static class NativeApi
+    {
+        [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
+        public static extern int MessageBox(IntPtr hWnd, String text, String caption, int options);
+
+        public static void LinuxMessageBox(string title, string msg, string type)
+        {
+            try
+            {
+                ProcessStartInfo p = new ProcessStartInfo("zenity", string.Format("--{0} --title=\"{1}\" --text=\"{2}\"", type, title.Replace("\"", "\\\""), msg.Replace("\"", "\\\"")));
+                p.CreateNoWindow = true;
+                p.ErrorDialog = false;
+                p.UseShellExecute = true;
+                var process = Process.Start(p);
+                process.WaitForExit();
+            }
+            catch { }
+        }
+
+        public static void ExitWithMessage(string title, string msg, int exitCode)
+        {
+            Console.Error.WriteLine(title + ": " + msg);
+            if (PlatformDetection.IsWindows)
+            {
+                MessageBox(IntPtr.Zero, msg, title, 0x10);
+            }
+            else if (PlatformDetection.IsMac)
+            {
+            }
+            else
+            {
+                LinuxMessageBox(title, msg + @" foo ""bar"" baz", "error");
+            }
+
+            Environment.Exit(exitCode);
         }
     }
 }