Refactor to its own class, UiSynchronizer.

Update description for better clarity.
Add calls to its Initialize method.

Author: bclothier

RetailCoder.VBE/API/VBA/ParserState.cs

@@ -56,6 +56,7 @@ public sealed class ParserState : IParserState, IDisposable
         public ParserState()
         {
             UiDispatcher.Initialize();
+            UiSynchronizer.Initialize();
         }
 
         public void Initialize(Microsoft.Vbe.Interop.VBE vbe)

RetailCoder.VBE/App.cs

@@ -50,6 +50,7 @@ public App(IVBE vbe,
             _configService.SettingsChanged += _configService_SettingsChanged;
 
             UiDispatcher.Initialize();
+            UiSynchronizer.Initialize();
         }
 
         private void _configService_SettingsChanged(object sender, ConfigurationChangedEventArgs e)

Rubberduck.Parsing/Rubberduck.Parsing.csproj

@@ -176,6 +176,7 @@
     <Compile Include="Symbols\ParsingExceptions\MainParseSyntaxErrorException.cs" />
     <Compile Include="Symbols\ParsingExceptions\PreprosessorSyntaxErrorException.cs" />
     <Compile Include="UIContext\UiDispatcher.cs" />
+    <Compile Include="UIContext\UiSynchronizer.cs" />
     <Compile Include="VBA\RepositoryProjectManager.cs" />
     <Compile Include="VBA\ParsePass.cs" />
     <Compile Include="Inspections\CannotAnnotateAttribute.cs" />

Rubberduck.Parsing/UIContext/UiDispatcher.cs

@@ -1,17 +1,11 @@
 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; }
@@ -104,8 +98,7 @@ public static Task<T> StartTask<T>(Func<T> func, TaskCreationOptions options = T
         {
             return StartTask(func, CancellationToken.None, options);
         }
-
-
+        
         private static void CheckInitialization()
         {
             if (UiContext == null) throw new InvalidOperationException("UiDispatcher is not initialized. Invoke Initialize() from UI thread first.");
@@ -119,81 +112,5 @@ 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. This should be used by the UI thread **ONLY**.
-        /// </summary>
-        /// <remarks>
-        /// Typical use would be within a event handler for an event belonging to a COM 
-        /// object which require some synchronization with COM accesses from other threads. 
-        /// Events raised by COM are on UI thread by definition. 
-        /// </remarks>
-        public static int DoEvents()
-        {
-            CheckInitialization();
-
-            if (UiContext != SynchronizationContext.Current)
-            {
-                throw new InvalidOperationException("DoEvents cannot be used in other threads");
-            }
-
-            return 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;
-        }
     }
 }

Rubberduck.Parsing/UIContext/UiSynchronizer.cs

@@ -0,0 +1,111 @@
+using System;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace Rubberduck.Parsing.UIContext
+{
+    public static class UiSynchronizer
+    {
+        private enum DllVersion
+        {
+            Unknown,
+            Vbe6,
+            Vbe7
+        }
+
+        private static DllVersion _version;
+
+        private static SynchronizationContext UiContext { get; set; }
+
+        static UiSynchronizer()
+        {
+            _version = DllVersion.Unknown;
+        }
+
+        public static void Initialize()
+        {
+            if (UiContext == null)
+            {
+                UiContext = SynchronizationContext.Current;
+            }
+        }
+
+        /// <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. This should be used by the UI thread **ONLY**; 
+        /// otherwise execptions will be thrown.
+        /// </summary>
+        /// <remarks>
+        /// Typical use would be within a event handler for an event belonging to a COM 
+        /// object which require some synchronization with COM accesses from other threads. 
+        /// Events raised by COM are on UI thread by definition so the call stack originating
+        /// from COM objects' events can use this method.
+        /// </remarks>
+        /// <returns>Count of open forms which is always zero for VBA hosts but may be nonzero for VB6 projects.</returns>
+        public static int DoEvents()
+        {
+            CheckContext();
+            
+            return ExecuteDoEvents();
+        }
+
+        private static int ExecuteDoEvents()
+        {
+            switch (_version)
+            {
+                case DllVersion.Vbe7:
+                    return rtcDoEvents7();
+                case DllVersion.Vbe6:
+                    return rtcDoEvents6();
+                default:
+                    return DetermineVersionAndExecute();
+            }
+        }
+
+        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.... Rubberduck is a VBA add-in, so how the heck could it have loaded without a VBE dll?!?
+                    throw new InvalidOperationException("Cannot execute DoEvents; the VBE dll could not be located.");
+                }
+            }
+
+            return result;
+        }
+
+        private static void CheckContext()
+        {
+            if (UiContext == null)
+            {
+                throw new InvalidOperationException("UiSynchronizer is not initialized. Invoke Initialize() from UI thread first.");
+            }
+            
+            if (UiContext != SynchronizationContext.Current)
+            {
+                throw new InvalidOperationException("UiSynchronizer cannot be used in other threads. Only the UI thread can call methods on the UiSynchronizer");
+            }
+        }
+
+        [DllImport("vbe6.dll", EntryPoint = "rtcDoEvents")]
+        private static extern int rtcDoEvents6();
+
+        [DllImport("vbe7.dll", EntryPoint = "rtcDoEvents")]
+        private static extern int rtcDoEvents7();
+    }
+}