WpfWorkbench.OnDrop: don't show dialogs during the drop event; use Dispatcher.BeginInvoke instead.

src/Libraries/NRefactory/ICSharpCode.NRefactory.CSharp/Resolver/CSharpResolver.cs

@@ -1694,8 +1694,7 @@ namespace ICSharpCode.NRefactory.CSharp.Resolver
 				case NameLookupMode.Type:
 				case NameLookupMode.TypeInUsingDeclaration:
 				case NameLookupMode.BaseTypeReference:
-					result = lookup.LookupType(target.Type, identifier, typeArguments, parameterizeResultType);
-					break;
+					return lookup.LookupType(target.Type, identifier, typeArguments, parameterizeResultType);
 				default:
 					throw new NotSupportedException("Invalid value for NameLookupMode");
 			}

src/Main/Core/Project/Src/Services/FileUtility/FileUtility.cs

@@ -648,6 +648,7 @@ namespace ICSharpCode.Core
 
 		static FileOperationResult ObservedSaveHandleError(Exception e, NamedFileOperationDelegate saveFileAs, FileName fileName, string message, FileErrorPolicy policy)
 		{
+			message = message + Environment.NewLine + Environment.NewLine + e.Message;
 			var messageService = ServiceSingleton.GetRequiredService<IMessageService>();
 			switch (policy) {
 				case FileErrorPolicy.Inform:
@@ -693,6 +694,7 @@ namespace ICSharpCode.Core
 
 		static FileOperationResult ObservedLoadHandleException(Exception e, FileOperationDelegate loadFile, FileName fileName, string message, FileErrorPolicy policy)
 		{
+			message = message + Environment.NewLine + Environment.NewLine + e.Message;
 			var messageService = ServiceSingleton.GetRequiredService<IMessageService>();
 			switch (policy) {
 				case FileErrorPolicy.Inform:

src/Main/SharpDevelop/Workbench/WpfWorkbench.cs

@@ -671,6 +671,17 @@ namespace ICSharpCode.SharpDevelop.Workbench
 					string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
 					if (files == null)
 						return;
+					// Handle opening the files outside the drop event, so that the drag source doesn't think
+					// the operation is still in progress while we're showing a "file cannot be opened" error message.
+					Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action<string[]>(HandleDrop), files);
+				}
+			} catch (Exception ex) {
+				MessageService.ShowException(ex);
+			}
+		}
+		
+		void HandleDrop(string[] files)
+		{
 			foreach (string file in files) {
 				if (File.Exists(file)) {
 					var fileName = FileName.Create(file);
@@ -682,10 +693,6 @@ namespace ICSharpCode.SharpDevelop.Workbench
 				}
 			}
 		}
-			} catch (Exception ex) {
-				MessageService.ShowException(ex);
-			}
-		}
 		
 		void InitFocusTrackingEvents()
 		{