C#实现的下拉多选框，下拉多选树，多级节点

[ToolboxItem(true)]     public partial class DropDownTreeViewControl : RadControl     {         public DropDownTreeViewElement TreeViewElement { get; private set; }          public RadTreeView TreeViewControl         {             get             {                 return this.TreeViewElement.TreeViewControl;             }         }          protected override void CreateChildItems(RadElement parent)         {             this.AllowShowFocusCues = true;              base.CreateChildItems(parent);              this.TreeViewElement = new DropDownTreeViewElement();              parent.Children.Add(TreeViewElement);          }          protected override void OnEnter(EventArgs e)         {             base.OnEnter(e);             this.TreeViewElement.Focus();         }          protected override void OnBindingContextChanged(EventArgs e)         {             base.OnBindingContextChanged(e);              this.TreeViewControl.BindingContext = this.BindingContext;         }          public class DropDownTreeViewElement : LightVisualElement         {             private readonly Color BG_COLOR = Color.White;             private readonly Color BORDER_COLOR = Color.LightBlue;             private readonly Color ARROW_BORDER_COLOR = Color.LightGray;             private readonly Color ARROW_NORMAL_BG_COLOR = Color.White;             private readonly Color ARROW_MOUSE_OVER_BG_COLOR = Color.LightYellow;             private readonly Color ARROW_PRESSED_BG_COLOR = Color.DarkOrange;              private readonly int NORMAL_BORDER_WIDTH = 1;             private readonly int FOCUS_BORDER_WIDTH = 2;              private RadArrowButtonElement arrow;             private PopupForm popup;             private bool isInnerCallHide;              public bool IsPopupOpen { get; private set; }             public RadTreeView TreeViewControl             {                 get                 {                     return this.popup.TreeView;                 }             }              protected override void InitializeFields()             {                 base.InitializeFields();                  // style                 this.DrawBorder = true;                 this.BorderBoxStyle = BorderBoxStyle.SingleBorder;                 this.BorderGradientStyle = GradientStyles.Solid;                 this.BorderColor = BORDER_COLOR;                 this.DrawFill = true;                 this.NumberOfColors = 1;                 this.GradientStyle = GradientStyles.Solid;                 this.BackColor = BG_COLOR;                 this.StretchHorizontally = true;                 this.StretchVertically = true;             }              protected override void CreateChildElements()             {                 base.CreateChildElements();                  // arrow                 this.CreateArrow();                  // popup                 this.CreatePopup();                  this.Children.Add(arrow);             }              private void CreatePopup()             {                 this.popup = new PopupForm(this);                 this.popup.PopupClosing += Popup_PopupClosing;                 this.popup.PopupClosed += Popup_PopupClosed;             }              private void Popup_PopupClosing(object sender, RadPopupClosingEventArgs args)             {                 // mouse postion in control-bounds prevent                 if (args.CloseReason == RadPopupCloseReason.Mouse)                 {                     var boundsSc = RectangleToScreen(this.Bounds);                     if (boundsSc.Contains(MousePosition))                     {                         args.Cancel = true;                     }                 }             }              private void Popup_PopupClosed(object sender, RadPopupClosedEventArgs args)             {                 if (isInnerCallHide)                 {                     return;                 }                 this.IsPopupOpen = false;                 this.SwitchArrowState(false);             }              private void CreateArrow()             {                 this.arrow = new RadArrowButtonElement()                 {                     ClickMode = ClickMode.Press,                     MinSize = new Size(SystemInformation.VerticalScrollBarWidth,                                     RadArrowButtonElement.RadArrowButtonDefaultSize.Height),                     StretchHorizontally = false,                     StretchVertically = true,                     Margin = new System.Windows.Forms.Padding(2),                 };                  arrow.Fill.NumberOfColors = 1;                 arrow.Fill.BackColor = ARROW_NORMAL_BG_COLOR;                 arrow.Border.BoxStyle = BorderBoxStyle.SingleBorder;                 arrow.Border.GradientStyle = GradientStyles.Solid;                 arrow.Border.ForeColor = ARROW_BORDER_COLOR;                  arrow.RadPropertyChanged += Arrow_RadPropertyChanged;                 arrow.Click += Arrow_Click;             }              private void Arrow_Click(object sender, EventArgs e)             {                 if (this.IsPopupOpen)                 {                     this.IsPopupOpen = false;                     this.SwitchArrowState(false);                     this.HidePopup();                 }                 else                 {                     this.IsPopupOpen = true;                     this.SwitchArrowState(true);                     this.ShowPopup();                 }             }              private void HidePopup()             {                 this.isInnerCallHide = true;                 this.popup.Hide();                 this.isInnerCallHide = false;             }              private void ShowPopup()             {                 this.popup.Width = this.Bounds.Width;                 this.popup.Height = 250;                 this.popup.ShowPopup(this.RectangleToScreen(this.ControlBoundingRectangle));             }              private void SwitchArrowState(bool isPressed)             {                 this.arrow.Fill.BackColor = isPressed ? ARROW_PRESSED_BG_COLOR :                     (arrow.IsMouseOver ? ARROW_MOUSE_OVER_BG_COLOR : ARROW_NORMAL_BG_COLOR);             }              protected override void OnPropertyChanged(RadPropertyChangedEventArgs e)             {                 if (e.Property == ContainsFocusProperty)                 {                     var isFocus = (bool)e.NewValue;                     this.BorderWidth = isFocus ? FOCUS_BORDER_WIDTH : NORMAL_BORDER_WIDTH;                 }                  base.OnPropertyChanged(e);             }              protected override SizeF ArrangeOverride(SizeF finalSize)             {                 base.ArrangeOverride(finalSize);                  // arrow on right side                 float width = this.arrow.DesiredSize.Width;                 float x = this.RightToLeft ? 0f : (finalSize.Width - width);                 RectangleF finalRect = new RectangleF(x, 0f, width, finalSize.Height);                 this.arrow.Arrange(finalRect);                  return finalSize;             }              private void Arrow_RadPropertyChanged(object sender, RadPropertyChangedEventArgs e)             {                 if (e.Property == RadArrowButtonElement.IsMouseOverProperty)                 {                     if (this.IsPopupOpen)                     {                         return;                     }                      var arrow = sender as RadArrowButtonElement;                     var isMouseOver = (bool)e.NewValue;                      arrow.Fill.BackColor = isMouseOver ? ARROW_MOUSE_OVER_BG_COLOR : ARROW_NORMAL_BG_COLOR;                 }             }          }          public class PopupForm : RadSizablePopupControl         {             private HostTreeView tv;              public PopupForm(RadItem owner)                 : base(owner)             {                 this.SizingMode = SizingMode.UpDownAndRightBottom;                 this.VerticalAlignmentCorrectionMode = AlignmentCorrectionMode.SnapToOuterEdges;             }              public RadTreeView TreeView             {                 get                 {                     return this.tv.TreeView;                 }             }              protected override void CreateChildItems(RadElement parent)             {                 base.CreateChildItems(parent);                  this.tv = new HostTreeView();                 this.tv.TreeView.Focusable = false;                 this.tv.TreeView.CheckBoxes = true;                 this.SizingGripDockLayout.Children.Add(tv);             }               public override bool OnMouseWheel(Control target, int delta)             {                 if (delta < 0)                 {                     this.tv.TreeView.VScrollBar.PerformSmallIncrement(1);                 }                 else                 {                     this.tv.TreeView.VScrollBar.PerformSmallDecrement(1);                 }                  return true;             }         }          public class HostTreeView : Telerik.WinControls.RadHostItem         {             public HostTreeView()                 : base(new RadTreeView())             {              }              public RadTreeView TreeView             {                 get                 {                     return this.HostedControl as RadTreeView;                 }             }         }     }