Re-read MSBuild items list when target framework is changed.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@5939 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/Main/Base/Project/Src/Project/CompilableProject.cs

@@ -377,6 +377,8 @@ namespace ICSharpCode.SharpDevelop.Project
 		protected override void OnPropertyChanged(ProjectPropertyChangedEventArgs e)
 		{
 			base.OnPropertyChanged(e);
+			if (e.PropertyName == "TargetFrameworkVersion")
+				CreateItemsListFromMSBuild();
 			if (!isLoading) {
 				if (reparseReferencesSensitiveProperties.Contains(e.PropertyName)) {
 					ParserService.Reparse(this, true, false);