Initial version for providing equivalent to DoEvents to allow pumping of message pumps in VBE thread for COM object marshalling.

Author: bclothier

Rubberduck.Parsing/UIContext/UiDispatcher.cs

@@ -1,11 +1,17 @@
 using System;
+using System.Runtime.InteropServices;
 using System.Threading;
 using System.Threading.Tasks;
 
 namespace Rubberduck.Parsing.UIContext
 {
     public static class UiDispatcher
     {
+        static UiDispatcher()
+        {
+            _version = DllVersion.Unknown;
+        }
+
         // thanks to Pellared on http://stackoverflow.com/a/12909070/1188513
 
         private static SynchronizationContext UiContext { get; set; }
@@ -113,5 +119,69 @@ public static void Shutdown()
             //    Dispatcher.CurrentDispatcher.InvokeShutdown();
             //});
         }
+
+        /// <summary>
+        /// Used to pump any pending COM messages. This should be used only as a part of
+        /// synchronizing or to effect a block until all other threads has finished with 
+        /// their pending COM calls. 
+        /// </summary>
+        public static void DoEvents()
+        {
+            Invoke(() => ExecuteDoEvents());
+        }
+
+        private static int ExecuteDoEvents()
+        {
+            switch (_version)
+            {
+                case DllVersion.Vbe7:
+                    return rtcDoEvents7();
+                case DllVersion.Vbe6:
+                    return rtcDoEvents6();
+                default:
+                    return DetermineVersionAndExecute();
+            }
+        }
+
+        private enum DllVersion
+        {
+            Unknown,
+            Vbe6,
+            Vbe7
+        }
+
+        private static DllVersion _version;
+        
+        [DllImport("vbe6.dll", EntryPoint = "rtcDoEvents")]
+        private static extern int rtcDoEvents6();
+
+        [DllImport("vbe7.dll", EntryPoint = "rtcDoEvents")]
+        private static extern int rtcDoEvents7();
+        
+        private static int DetermineVersionAndExecute()
+        {
+            int result;
+            try
+
+            {
+                result = rtcDoEvents7();
+                _version = DllVersion.Vbe7;
+            }
+            catch
+            {
+                try
+                {
+                    result = rtcDoEvents6();
+                    _version = DllVersion.Vbe6;
+                }
+                catch
+                {
+                    // we shouldn't be here....
+                    throw new InvalidOperationException("Cannot execute DoEvents; the VBE dll could not be located.");
+                }
+            }
+
+            return result;
+        }
     }
 }