Refactor DropSourceBehaviour and related code to replace ArrayList wi…

…th List<T>

src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/Behavior/ContainerSelectorBehavior.cs

@@ -207,7 +207,7 @@ private void StartDragOperation(Point initialMouseLocation)
 
             //must identify a required parent to avoid dragging mixes of children
             Control requiredParent = _containerControl.Parent;
-            ArrayList dragControls = new ArrayList();
+            List<IComponent> dragControls = new();
             ICollection selComps = selSvc.GetSelectedComponents();
             //create our list of controls-to-drag
             foreach (IComponent comp in selComps)

src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/Behavior/DropSourceBehavior.cs

@@ -19,7 +19,7 @@ internal sealed partial class DropSourceBehavior : Behavior, IComparer
     {
         private struct DragComponent
         {
-            public object dragComponent; //the dragComponent
+            public IComponent dragComponent; //the dragComponent
             public int zorderIndex; //the dragComponent's z-order index
             public Point originalControlLocation; //the original control of the control in AdornerWindow coordinates
             public Point draggedLocation; //the location of the component after each drag - in AdornerWindow coordinates
@@ -72,9 +72,9 @@ private struct DragComponent
         private int primaryComponentIndex = -1; // Index of the primary component (control) in dragComponents
 
         /// <summary>
-        ///  Constuctor that caches all needed vars for perf reasons.
+        ///  Constructor that caches all needed variables for perf reasons.
         /// </summary>
-        internal DropSourceBehavior(ICollection dragComponents, Control source, Point initialMouseLocation)
+        internal DropSourceBehavior(List<IComponent> dragComponents, Control source, Point initialMouseLocation)
         {
             serviceProviderSource = source.Site;
             if (serviceProviderSource is null)
@@ -321,7 +321,7 @@ private void EndDragDrop(bool allowSetChildIndexOnDrop)
             }
 
             // We use this list when doing a Drag-Copy, so that we can correctly restore state when we are done. See Copy code below.
-            ArrayList originalControls = null;
+            List<IComponent> originalControls = null;
             bool performCopy = (lastEffect == DragDropEffects.Copy);
 
             Control dragSource = data.Source;
@@ -385,21 +385,21 @@ private void EndDragDrop(bool allowSetChildIndexOnDrop)
                             numberOfOriginalTrayControls = tray is not null ? tray.Controls.Count : 0;
 
                             // Get the objects to copy
-                            ArrayList temp = new ArrayList();
+                            List<IComponent> temp = new();
                             for (int i = 0; i < dragComponents.Length; i++)
                             {
                                 temp.Add(dragComponents[i].dragComponent);
                             }
 
                             // Create a copy of them
-                            temp = DesignerUtils.CopyDragObjects(temp, serviceProviderTarget) as ArrayList;
+                            temp = DesignerUtils.CopyDragObjects(temp, serviceProviderTarget).Cast<IComponent>().ToList();
                             if (temp is null)
                             {
                                 Debug.Fail("Couldn't create copies of the controls we are dragging.");
                                 return;
                             }
 
-                            originalControls = new ArrayList();
+                            originalControls = new();
                             // And stick the copied controls back into the dragComponents array
                             for (int j = 0; j < temp.Count; j++)
                             {
@@ -885,9 +885,9 @@ private void DisableAdorners(IServiceProvider serviceProvider, BehaviorService b
         /// <summary>
         ///  Called when the ControlDesigner starts a drag operation. Here, all adorners are disabled, screen shots of all related controls are taken, and the DragAssistanceManager  (for SnapLines) is created.
         /// </summary>
-        private void InitiateDrag(Point initialMouseLocation, ICollection dragComps)
+        private void InitiateDrag(Point initialMouseLocation, ICollection<IComponent> dragComps)
         {
-            dragObjects = dragComps.Cast<IComponent>().ToList();
+            dragObjects = dragComps.ToList();
             DisableAdorners(serviceProviderSource, behaviorServiceSource, false);
             Control primaryControl = dragObjects[0] as Control;
             Control primaryParent = primaryControl?.Parent;

src/System.Windows.Forms.Design/src/System/Windows/Forms/Design/Behavior/SelectionManager.cs

@@ -66,7 +66,7 @@ public SelectionManager(IServiceProvider serviceProvider, BehaviorService behavi
             _bodyAdorner = new Adorner();
             behaviorService.Adorners.Add(_bodyAdorner);
             behaviorService.Adorners.Add(_selectionAdorner); //adding this will cause the adorner to get setup with a ptr
-                                                            //to the beh.svc.
+                                                             //to the beh.svc.
 
             _componentToDesigner = new Hashtable();
 
@@ -282,17 +282,13 @@ private void OnComponentAdded(object source, ComponentEventArgs ce)
         /// </summary>
         private void OnBeginDrag(object source, BehaviorDragDropEventArgs e)
         {
-            ArrayList dragComps = new ArrayList(e.DragComponents);
-            ArrayList glyphsToRemove = new ArrayList();
+            List<IComponent> dragComps = e.DragComponents.Cast<IComponent>().ToList();
+            List<Glyph> glyphsToRemove = new();
             foreach (ControlBodyGlyph g in _bodyAdorner.Glyphs)
             {
-                if (g.RelatedComponent is Control)
+                if (g.RelatedComponent is Control control && (dragComps.Contains(g.RelatedComponent) || !control.AllowDrop))
                 {
-                    if (dragComps.Contains(g.RelatedComponent) ||
-                        !((Control)g.RelatedComponent).AllowDrop)
-                    {
-                        glyphsToRemove.Add(g);
-                    }
+                    glyphsToRemove.Add(g);
                 }
             }