fix error when the file is deleted.

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/AvalonEditViewContent.cs

@@ -60,12 +60,14 @@ namespace ICSharpCode.AvalonEdit.AddIn
 		void OnFileExternallyChanged(object sender, EventArgs e)
 		{
 			// handle readonly
+			if (this.PrimaryFileName != null && File.Exists(this.PrimaryFileName)) {
 				bool isExternalReadOnly = (File.GetAttributes(this.PrimaryFileName) & FileAttributes.ReadOnly) == FileAttributes.ReadOnly;
 				if (isExternalReadOnly != IsReadOnly) {
 					codeEditor.PrimaryTextEditor.IsReadOnly = isExternalReadOnly;
 					OnIsReadOnlyChanged(EventArgs.Empty);
 				}
 			}
+		}
 		
 		void codeEditor_Document_UndoStack_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
 		{

src/Main/Base/Project/Src/Services/File/FileChangeWatcher.cs

@@ -9,6 +9,7 @@ using System.Windows.Forms;
 
 using ICSharpCode.Core;
 using ICSharpCode.SharpDevelop.Gui;
+using ICSharpCode.SharpDevelop.Project;
 
 namespace ICSharpCode.SharpDevelop
 {
@@ -162,6 +163,7 @@ namespace ICSharpCode.SharpDevelop
 					watcher.Changed += OnFileChangedEvent;
 					watcher.Created += OnFileChangedEvent;
 					watcher.Renamed += OnFileChangedEvent;
+					watcher.Deleted += OnFileChangedEvent;
 				}
 				watcher.Path = Path.GetDirectoryName(fileName);
 				watcher.Filter = Path.GetFileName(fileName);
@@ -196,11 +198,16 @@ namespace ICSharpCode.SharpDevelop
 				wasChangedExternally = true;
 				OnFileChanged(EventArgs.Empty);
 				
-				// if the file was only made readonly, don't prevent reloading it from disk
+				if (System.IO.File.Exists(this.file.FileName)) {
+					// if the file was only made readonly, prevent reloading it from disk
 					bool readOnly = (System.IO.File.GetAttributes(this.file.FileName) & FileAttributes.ReadOnly) == FileAttributes.ReadOnly;
 					if (readOnly != isFileReadOnly)
 						wasChangedExternally = false;
 					isFileReadOnly = readOnly;
+				} else {
+					// use to raise the events
+					FileService.RemoveFile(this.file.FileName, false);
+				}
 				
 				if (WorkbenchSingleton.Workbench.IsActiveWindow) {
 					// delay reloading message a bit, prevents showing two messages