WPF Designer: Fixed "Cannot move multiple controls" (http://community.sharpdevelop.net/forums/t/13250.aspx)

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Project/Services/DragMoveMouseGesture.cs

@@ -16,13 +16,15 @@ namespace ICSharpCode.WpfDesign.Designer.Services
 	sealed class DragMoveMouseGesture : ClickOrDragMouseGesture
 	{
 		bool isDoubleClick;
+		bool setSelectionIfNotMoving;
 		MoveLogic moveLogic;
 		
-		internal DragMoveMouseGesture(DesignItem clickedOn, bool isDoubleClick)
+		internal DragMoveMouseGesture(DesignItem clickedOn, bool isDoubleClick, bool setSelectionIfNotMoving = false)
 		{
 			Debug.Assert(clickedOn != null);
 			
 			this.isDoubleClick = isDoubleClick;
+			this.setSelectionIfNotMoving = setSelectionIfNotMoving;
 			this.positionRelativeTo = clickedOn.Services.DesignPanel;
 
 			moveLogic = new MoveLogic(clickedOn);
@@ -41,10 +43,14 @@ namespace ICSharpCode.WpfDesign.Designer.Services
 		
 		protected override void OnMouseUp(object sender, MouseButtonEventArgs e)
 		{
-			if (!hasDragStarted && isDoubleClick) {
-				// user made a double-click
-				Debug.Assert(moveLogic.Operation == null);
-				moveLogic.HandleDoubleClick();
+			if (!hasDragStarted) {
+				if (isDoubleClick) {
+					// user made a double-click
+					Debug.Assert(moveLogic.Operation == null);
+					moveLogic.HandleDoubleClick();
+				} else if (setSelectionIfNotMoving) {
+					services.Selection.SetSelectedComponents(new DesignItem[] { moveLogic.ClickedOn }, SelectionTypes.Auto);
+				}
 			}
 			moveLogic.Stop();
 			Stop();

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Project/Services/PointerTool.cs

@@ -37,9 +37,18 @@ namespace ICSharpCode.WpfDesign.Designer.Services
 					if (e.ChangedButton == MouseButton.Left && MouseGestureBase.IsOnlyButtonPressed(e, MouseButton.Left)) {
 						e.Handled = true;
 						ISelectionService selectionService = designPanel.Context.Services.Selection;
-						selectionService.SetSelectedComponents(new DesignItem[] { result.ModelHit }, SelectionTypes.Auto);
+						bool setSelectionIfNotMoving = false;
 						if (selectionService.IsComponentSelected(result.ModelHit)) {
-							new DragMoveMouseGesture(result.ModelHit, e.ClickCount == 2).Start(designPanel, e);
+							setSelectionIfNotMoving = true;
+							// There might be multiple components selected. We might have
+							// to set the selection to only the item clicked on
+							// (or deselect the item clicked on if Ctrl is pressed),
+							// but we should do so only if the user isn't performing a drag operation.
+						} else {
+							selectionService.SetSelectedComponents(new DesignItem[] { result.ModelHit }, SelectionTypes.Auto);
+						}
+						if (selectionService.IsComponentSelected(result.ModelHit)) {
+							new DragMoveMouseGesture(result.ModelHit, e.ClickCount == 2, setSelectionIfNotMoving).Start(designPanel, e);
 						}
 					}
 				}