[API Proposal]: add ToolStripItem.SelectedChanged event dotnet#8548 (d…

…otnet#10321)

src/System.Windows.Forms/src/PublicAPI.Unshipped.txt

@@ -25,8 +25,10 @@ System.Windows.Forms.ListViewGroupCollection.AddRange(params System.Windows.Form
 System.Windows.Forms.ListViewItem.ListViewSubItemCollection.AddRange(params string![]! items) -> void
 System.Windows.Forms.ListViewItem.ListViewSubItemCollection.AddRange(params System.Windows.Forms.ListViewItem.ListViewSubItem![]! items) -> void
 System.Windows.Forms.TabControl.TabPageCollection.AddRange(params System.Windows.Forms.TabPage![]! pages) -> void
+System.Windows.Forms.ToolStripItem.SelectedChanged -> System.EventHandler?
 System.Windows.Forms.ToolStripItemCollection.AddRange(params System.Windows.Forms.ToolStripItem![]! toolStripItems) -> void
 System.Windows.Forms.ToolStripPanel.ToolStripPanelRowCollection.AddRange(params System.Windows.Forms.ToolStripPanelRow![]! value) -> void
 virtual System.Windows.Forms.Control.ControlCollection.AddRange(params System.Windows.Forms.Control![]! controls) -> void
 virtual System.Windows.Forms.ListView.ColumnHeaderCollection.AddRange(params System.Windows.Forms.ColumnHeader![]! values) -> void
+virtual System.Windows.Forms.ToolStripItem.OnSelectedChanged(System.EventArgs! e) -> void
 virtual System.Windows.Forms.TreeNodeCollection.AddRange(params System.Windows.Forms.TreeNode![]! nodes) -> void

src/System.Windows.Forms/src/Resources/SR.resx

@@ -5889,6 +5889,9 @@ Stack trace where the illegal operation occurred was:
   <data name="ToolStripItemsDescr" xml:space="preserve">
     <value>Collection of items to display on the ToolStrip.</value>
   </data>
+  <data name="ToolStripItemSelectedChangedDescr" xml:space="preserve">
+    <value>Occurs when the Selected property value changes.</value>
+  </data>
   <data name="ToolStripItemSize" xml:space="preserve">
     <value>The size of the item.</value>
   </data>

src/System.Windows.Forms/src/System/Windows/Forms/Controls/ToolStrips/ToolStripItem.cs

@@ -89,6 +89,7 @@ public abstract partial class ToolStripItem :
     internal static readonly object s_ownerChangedEvent = new();
     internal static readonly object s_paintEvent = new();
     internal static readonly object s_textChangedEvent = new();
+    internal static readonly object s_selectedChangedEvent = new();
 
     internal static readonly object s_commandChangedEvent = new();
     internal static readonly object s_commandParameterChangedEvent = new();
@@ -314,7 +315,7 @@ public ToolStripItemAlignment Alignment
     /// <summary>
     ///  Determines if this item can be dragged.
     ///  This is EXACTLY like Control.AllowDrop - setting this to true WILL call
-    ///  the droptarget handlers. The ToolStripDropTargetManager is the one that
+    ///  the dropTarget handlers. The ToolStripDropTargetManager is the one that
     ///  handles the routing of DropTarget events to the ToolStripItem's IDropTarget
     ///  methods.
     /// </summary>
@@ -845,6 +846,7 @@ public virtual bool Enabled
                     if (wasSelected)
                     {
                         KeyboardToolTipStateMachine.Instance.NotifyAboutLostFocus(this);
+                        OnSelectedChanged(EventArgs.Empty);
                     }
                 }
 
@@ -1429,7 +1431,7 @@ public event MouseEventHandler? MouseUp
 
     /// <summary>
     ///  Name of this control. The designer will set this to the same
-    ///  as the programatic Id "(name)" of the control. The name can be
+    ///  as the programmatic Id "(name)" of the control. The name can be
     ///  used as a key into the ControlCollection.
     /// </summary>
     [Browsable(false)]
@@ -1449,7 +1451,7 @@ public string? Name
     }
 
     /// <summary>
-    ///  The owner of this ToolStripItem. The owner is essentially a backpointer to
+    ///  The owner of this ToolStripItem. The owner is essentially a backPointer to
     ///  the ToolStrip who contains this item in it's item collection. Handy for getting
     ///  to things such as the ImageList, which would be defined on the ToolStrip.
     /// </summary>
@@ -1470,7 +1472,7 @@ public ToolStrip? Owner
     }
 
     /// <summary>
-    ///  Returns the "parent" item on the preceeding menu which has spawned this item.
+    ///  Returns the "parent" item on the preceding menu which has spawned this item.
     ///  e.g. File->Open  the OwnerItem of Open is File.
     /// </summary>
     [Browsable(false)]
@@ -1819,6 +1821,18 @@ public virtual bool Selected
             (ParentInternal is not null && ParentInternal.IsSelectionSuspended &&
              ParentInternal.LastMouseDownedItem == this));
 
+    /// <summary>
+    ///  Occurs when selected item changed.
+    /// </summary>
+    [SRDescription(nameof(SR.ToolStripItemSelectedChangedDescr))]
+    public event EventHandler? SelectedChanged
+    {
+        add => Events.AddHandler(s_selectedChangedEvent, value);
+        remove => Events.RemoveHandler(s_selectedChangedEvent, value);
+    }
+
+    protected virtual void OnSelectedChanged(EventArgs e) => RaiseEvent(s_selectedChangedEvent, e);
+
     protected internal virtual bool ShowKeyboardCues
         => DesignMode || ToolStripManager.ShowMenuFocusCues;
 
@@ -2222,7 +2236,7 @@ public DragDropEffects DoDragDrop(object data, DragDropEffects allowedEffects, B
                 iwdata.SetData(data);
             }
 
-            dataObject = (IComDataObject)iwdata;
+            dataObject = iwdata;
         }
 
         DROPEFFECT finalEffect;
@@ -2565,10 +2579,16 @@ private void HandleLeave()
     {
         if (_state[s_stateMouseDownAndNoDrag] || _state[s_statePressed] || _state[s_stateSelected])
         {
+            bool wasSelected = _state[s_stateSelected];
             _state[s_stateMouseDownAndNoDrag | s_statePressed | s_stateSelected] = false;
 
             KeyboardToolTipStateMachine.Instance.NotifyAboutLostFocus(this);
 
+            if (wasSelected)
+            {
+                OnSelectedChanged(EventArgs.Empty);
+            }
+
             Invalidate();
         }
     }
@@ -3229,6 +3249,8 @@ internal void Select(bool forceRaiseAccessibilityFocusChanged)
 
             KeyboardToolTipStateMachine.Instance.NotifyAboutGotFocus(this);
 
+            OnSelectedChanged(EventArgs.Empty);
+
             forceRaiseAccessibilityFocusChanged = true;
         }
 
@@ -3621,6 +3643,8 @@ internal void Unselect()
 
                 KeyboardToolTipStateMachine.Instance.NotifyAboutLostFocus(this);
             }
+
+            OnSelectedChanged(EventArgs.Empty);
         }
     }
 

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/ToolStripItemTests.cs

@@ -15398,6 +15398,55 @@ public void ToolStripItem_IDropTargetOnDragOver_Invoke_CallsDragOver(DragEventAr
         Assert.Equal(1, callCount);
     }
 
+    // Unit test for https://github.com/dotnet/winforms/issues/8548
+    [WinFormsFact]
+    public void ToolStripItem_OnItemSelected()
+    {
+        using MyMenuStrip menuStrip1 = new();
+        using ToolStripMenuItem toolStripMenuItem1 = new();
+        using ToolStripMenuItem toolStripMenuItem2 = new();
+        using ToolStripMenuItem toolStripMenuItem3 = new();
+
+        menuStrip1.Size = new Size(50, 100);
+        toolStripMenuItem1.Size = new Size(15, 30);
+        toolStripMenuItem2.Size = new Size(15, 30);
+        toolStripMenuItem3.Size = new Size(15, 30);
+
+        bool callBackInvoked = false;
+
+        toolStripMenuItem2.SelectedChanged += (e, s) =>
+        {
+            callBackInvoked = true;
+        };
+
+        menuStrip1.Items.AddRange(new ToolStripMenuItem[] { toolStripMenuItem1, toolStripMenuItem2, toolStripMenuItem3 });
+
+        menuStrip1.CreateControl();
+
+        // try to emulate mouse move event.
+        for (int i = 0; i < 10; i++)
+        {
+            menuStrip1.MoveMouse(new MouseEventArgs(MouseButtons.None, 0, new Point(i, 5)));
+        }
+
+        Assert.False(callBackInvoked);
+
+        for (int i = 10; i < 50; i++)
+        {
+            menuStrip1.MoveMouse(new MouseEventArgs(MouseButtons.None, 0, new Point(i, 5)));
+        }
+
+        Assert.True(callBackInvoked);
+    }
+
+    private class MyMenuStrip: MenuStrip
+    {
+        public void MoveMouse(MouseEventArgs mea)
+        {
+            OnMouseMove(mea);
+        }
+    }
+
     private class SubToolStrip : ToolStrip
     {
         public new void OnBeginDrag(EventArgs e) => base.OnBeginDrag(e);