c# 自定义多选下拉列表2

以下为工作中遇到的，备注一下

先需要几个辅助类

 #region GripBounds

 using System.Drawing;
 internal struct GripBounds
 {
     private const int GripSize = ;
     private const int CornerGripSize = GripSize << ;

     public GripBounds(Rectangle clientRectangle)
     {
         this.clientRectangle = clientRectangle;
     }

     private Rectangle clientRectangle;
     public Rectangle ClientRectangle
     {
         get { return clientRectangle; }
         //set { clientRectangle = value; }
     }

     public Rectangle Bottom
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.Y = rect.Bottom - GripSize + ;
             rect.Height = GripSize;
             return rect;
         }
     }

     public Rectangle BottomRight
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.Y = rect.Bottom - CornerGripSize + ;
             rect.Height = CornerGripSize;
             rect.X = rect.Width - CornerGripSize + ;
             rect.Width = CornerGripSize;
             return rect;
         }
     }

     public Rectangle Top
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.Height = GripSize;
             return rect;
         }
     }

     public Rectangle TopRight
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.Height = CornerGripSize;
             rect.X = rect.Width - CornerGripSize + ;
             rect.Width = CornerGripSize;
             return rect;
         }
     }

     public Rectangle Left
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.Width = GripSize;
             return rect;
         }
     }

     public Rectangle BottomLeft
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.Width = CornerGripSize;
             rect.Y = rect.Height - CornerGripSize + ;
             rect.Height = CornerGripSize;
             return rect;
         }
     }

     public Rectangle Right
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.X = rect.Right - GripSize + ;
             rect.Width = GripSize;
             return rect;
         }
     }

     public Rectangle TopLeft
     {
         get
         {
             Rectangle rect = ClientRectangle;
             rect.Width = CornerGripSize;
             rect.Height = CornerGripSize;
             return rect;
         }
     }
 }

 #endregion

 #region UnsafeMethods

 using System;
 using System.Drawing;
 using System.Runtime.InteropServices;
 internal class UnsafeMethods
 {
     public static readonly IntPtr TRUE = new IntPtr();
     public static readonly IntPtr FALSE = new IntPtr();

     public const int WM_LBUTTONDOWN = 0x201;
     public const int WM_RBUTTONDOWN = 0x204;
     public const int WM_MBUTTONDOWN = 0x207;
     public const int WM_NCLBUTTONDOWN = 0x0A1;
     public const int WM_NCRBUTTONDOWN = 0x0A4;
     public const int WM_NCMBUTTONDOWN = 0x0A7;
     public const int WM_NCCALCSIZE = 0x0083;
     public const int WM_NCHITTEST = 0x0084;
     public const int WM_NCPAINT = 0x0085;
     public const int WM_NCACTIVATE = 0x0086;
     public const int WM_MOUSELEAVE = 0x02A3;
     public const int WS_EX_NOACTIVATE = 0x08000000;
     public const int HTTRANSPARENT = -;
     public const int HTLEFT = ;
     public const int HTRIGHT = ;
     public const int HTTOP = ;
     public const int HTTOPLEFT = ;
     public const int HTTOPRIGHT = ;
     public const int HTBOTTOM = ;
     public const int HTBOTTOMLEFT = ;
     public const int HTBOTTOMRIGHT = ;
     public const int WM_USER = 0x0400;
     public const int WM_REFLECT = WM_USER + 0x1C00;
     public const int WM_COMMAND = 0x0111;
     public const int CBN_DROPDOWN = ;
     public const int WM_GETMINMAXINFO = 0x0024;

     public enum TrackerEventFlags : uint
     {
         TME_HOVER = 0x00000001,
         TME_LEAVE = 0x00000002,
         TME_QUERY = 0x40000000,
         TME_CANCEL = 0x80000000
     }

     [DllImport("user32.dll")]
     public static extern IntPtr GetWindowDC(IntPtr hWnd);

     [DllImport("user32.dll")]
     public static extern int ReleaseDC(IntPtr hwnd, IntPtr hDC);

     [DllImport("user32")]
     public static extern bool TrackMouseEvent(ref TRACKMOUSEEVENT lpEventTrack);

     [DllImport("user32.dll")]
     public static extern bool SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

     internal static int HIWORD(int n)
     {
         return (n >> ) & 0xffff;
     }

     internal static int HIWORD(IntPtr n)
     {
         return HIWORD(unchecked((int)(long)n));
     }

     internal static int LOWORD(int n)
     {
         return n & 0xffff;
     }

     internal static int LOWORD(IntPtr n)
     {
         return LOWORD(unchecked((int)(long)n));
     }

     [StructLayout(LayoutKind.Sequential)]
     internal struct TRACKMOUSEEVENT
     {
         public uint cbSize;
         public uint dwFlags;
         public IntPtr hwndTrack;
         public uint dwHoverTime;
     }

     [StructLayout(LayoutKind.Sequential)]
     internal struct MINMAXINFO
     {
         public Point reserved;
         public Size maxSize;
         public Point maxPosition;
         public Size minTrackSize;
         public Size maxTrackSize;
     }

     #region RECT structure

     [StructLayout(LayoutKind.Sequential)]
     internal struct RECT
     {
         public int left;
         public int top;
         public int right;
         public int bottom;

         public RECT(int left, int top, int right, int bottom)
         {
             this.left = left;
             this.top = top;
             this.right = right;
             this.bottom = bottom;
         }

         public Rectangle Rect
         {
             get
             {
                 return new Rectangle(
                     this.left,
                     this.top,
                     this.right - this.left,
                     this.bottom - this.top);
             }
         }

         public static RECT FromXYWH(int x, int y, int width, int height)
         {
             return new RECT(x,
                             y,
                             x + width,
                             y + height);
         }

         public static RECT FromRectangle(Rectangle rect)
         {
             return new RECT(rect.Left,
                              rect.Top,
                              rect.Right,
                              rect.Bottom);
         }
     }

     #endregion RECT structure

     #region WINDOWPOS

     [StructLayout(LayoutKind.Sequential)]
     internal struct WINDOWPOS
     {
         internal IntPtr hwnd;
         internal IntPtr hWndInsertAfter;
         internal int x;
         internal int y;
         internal int cx;
         internal int cy;
         internal uint flags;
     }
     #endregion

     #region NCCALCSIZE_PARAMS
     //http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowstructures/nccalcsize_params.asp
     [StructLayout(LayoutKind.Sequential)]
     public struct NCCALCSIZE_PARAMS
     {
         /// <summary>
         /// Contains the new coordinates of a window that has been moved or resized, that is, it is the proposed new window coordinates.
         /// </summary>
         public RECT rectProposed;
         /// <summary>
         /// Contains the coordinates of the window before it was moved or resized.
         /// </summary>
         public RECT rectBeforeMove;
         /// <summary>
         /// Contains the coordinates of the window's client area before the window was moved or resized.
         /// </summary>
         public RECT rectClientBeforeMove;
         /// <summary>
         /// Pointer to a WINDOWPOS structure that contains the size and position values specified in the operation that moved or resized the window.
         /// </summary>
         public WINDOWPOS lpPos;
     }

     #endregion
 }

 #endregion

 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
 using System.Drawing;
 using System.Drawing.Drawing2D;
 using System.Text;
 using System.Windows.Forms;
 using System.Security.Permissions;
 using System.Runtime.InteropServices;
 using VS = System.Windows.Forms.VisualStyles;

 /*
 <li>Base class for custom tooltips.</li>
 <li>Office-2007-like tooltip class.</li>
 */
 namespace ZhuoYueE.Bpc.Controls
 {
     /// <summary>
     /// Represents a pop-up window.
     /// </summary>
     [ToolboxItem(false)]
     public partial class PopupForm : ToolStripDropDown
     {
         #region " Fields & Properties "

         private Control content;
         /// <summary>
         /// Gets the content of the pop-up.
         /// </summary>
         public Control Content
         {
             get { return content; }
         }

         private bool fade;
         /// <summary>
         /// Gets a value indicating whether the <see cref="PopupControl.Popup"/> uses the fade effect.
         /// </summary>
         /// <value><c>true</c> if pop-up uses the fade effect; otherwise, <c>false</c>.</value>
         /// <remarks>To use the fade effect, the FocusOnOpen property also has to be set to <c>true</c>.</remarks>
         public bool UseFadeEffect
         {
             get { return fade; }
             set
             {
                 if (fade == value) return;
                 fade = value;
             }
         }

         private bool focusOnOpen = true;
         /// <summary>
         /// Gets or sets a value indicating whether the content should receive the focus after the pop-up has been opened.
         /// </summary>
         /// <value><c>true</c> if the content should be focused after the pop-up has been opened; otherwise, <c>false</c>.</value>
         /// <remarks>If the FocusOnOpen property is set to <c>false</c>, then pop-up cannot use the fade effect.</remarks>
         public bool FocusOnOpen
         {
             get { return focusOnOpen; }
             set { focusOnOpen = value; }
         }

         private bool acceptAlt = true;
         /// <summary>
         /// Gets or sets a value indicating whether presing the alt key should close the pop-up.
         /// </summary>
         /// <value><c>true</c> if presing the alt key does not close the pop-up; otherwise, <c>false</c>.</value>
         public bool AcceptAlt
         {
             get { return acceptAlt; }
             set { acceptAlt = value; }
         }

         private PopupForm ownerPopup;
         private PopupForm childPopup;

         private bool _resizable;
         private bool resizable;
         /// <summary>
         /// Gets or sets a value indicating whether the <see cref="PopupControl.Popup" /> is resizable.
         /// </summary>
         /// <value><c>true</c> if resizable; otherwise, <c>false</c>.</value>
         public bool Resizable
         {
             get { return resizable && _resizable; }
             set { resizable = value; }
         }

         private ToolStripControlHost host;

         private Size minSize;
         /// <summary>
         /// Gets or sets a minimum size of the pop-up.
         /// </summary>
         /// <returns>An ordered pair of type <see cref="T:System.Drawing.Size" /> representing the width and height of a rectangle.</returns>
         public new Size MinimumSize
         {
             get { return minSize; }
             set { minSize = value; }
         }

         private Size maxSize;
         /// <summary>
         /// Gets or sets a maximum size of the pop-up.
         /// </summary>
         /// <returns>An ordered pair of type <see cref="T:System.Drawing.Size" /> representing the width and height of a rectangle.</returns>
         public new Size MaximumSize
         {
             get { return maxSize; }
             set { maxSize = value; }
         }

         private bool _isOpen;

         public bool IsOpen
         {
             get { return _isOpen; }
         }

         /// <summary>
         /// Gets parameters of a new window.
         /// </summary>
         /// <returns>An object of type <see cref="T:System.Windows.Forms.CreateParams" /> used when creating a new window.</returns>
         protected override CreateParams CreateParams
         {
             [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
             get
             {
                 CreateParams cp = base.CreateParams;
                 cp.ExStyle |= UnsafeMethods.WS_EX_NOACTIVATE;
                 return cp;
             }
         }

         #endregion

         #region " Constructors "

         /// <summary>
         /// Initializes a new instance of the <see cref="PopupControl.Popup"/> class.
         /// </summary>
         /// <param name="content">The content of the pop-up.</param>
         /// <remarks>
         /// Pop-up will be disposed immediately after disposion of the content control.
         /// </remarks>
         /// <exception cref="T:System.ArgumentNullException"><paramref name="content" /> is <code>null</code>.</exception>
         public PopupForm(Control content)
         {
             if (content == null)
             {
                 throw new ArgumentNullException("content");
             }
             this.content = content;
             this.fade = SystemInformation.IsMenuAnimationEnabled && SystemInformation.IsMenuFadeEnabled;
             this._resizable = true;
             AutoSize = false;
             DoubleBuffered = true;
             ResizeRedraw = true;
             host = new ToolStripControlHost(content);
             Padding = Margin = host.Padding = host.Margin = Padding.Empty;
             MinimumSize = content.MinimumSize;
             content.MinimumSize = content.Size;
             MaximumSize = content.MaximumSize;
             content.MaximumSize = content.Size;
             Size = content.Size;
             content.Location = Point.Empty;
             Items.Add(host);
             content.Disposed += delegate(object sender, EventArgs e)
             {
                 content = null;
                 Dispose(true);
             };
             content.RegionChanged += delegate(object sender, EventArgs e)
             {
                 UpdateRegion();
             };
             content.Paint += delegate(object sender, PaintEventArgs e)
             {
                 PaintSizeGrip(e);
             };
             UpdateRegion();
         }

         #endregion

         #region " Methods "

         /// <summary>
         /// Processes a dialog box key.
         /// </summary>
         /// <param name="keyData">One of the <see cref="T:System.Windows.Forms.Keys" /> values that represents the key to process.</param>
         /// <returns>
         /// true if the key was processed by the control; otherwise, false.
         /// </returns>
         protected override bool ProcessDialogKey(Keys keyData)
         {
             if (acceptAlt && ((keyData & Keys.Alt) == Keys.Alt))
             {
                 if ((keyData & Keys.F4) != Keys.F4)
                 {
                     return false;
                 }
                 else
                 {
                     this.Close();
                 }
             }
             return base.ProcessDialogKey(keyData);
         }

         /// <summary>
         /// Updates the pop-up region.
         /// </summary>
         protected void UpdateRegion()
         {
             if (this.Region != null)
             {
                 this.Region.Dispose();
                 this.Region = null;
             }
             if (content.Region != null)
             {
                 this.Region = content.Region.Clone();
             }
         }

         /// <summary>
         /// Shows the pop-up window below the specified control.
         /// </summary>
         /// <param name="control">The control below which the pop-up will be shown.</param>
         /// <remarks>
         /// When there is no space below the specified control, the pop-up control is shown above it.
         /// </remarks>
         /// <exception cref="T:System.ArgumentNullException"><paramref name="control"/> is <code>null</code>.</exception>
         public void Show(Control control)
         {
             Show(control, control.ClientRectangle);
         }

         public void Show(Control control, bool center)
         {
             Show(control, control.ClientRectangle, center);
         }

         /// <summary>
         /// Shows the pop-up window below the specified area of the specified control.
         /// </summary>
         /// <param name="control">The control used to compute screen location of specified area.</param>
         /// <param name="area">The area of control below which the pop-up will be shown.</param>
         /// <remarks>
         /// When there is no space below specified area, the pop-up control is shown above it.
         /// </remarks>
         /// <exception cref="T:System.ArgumentNullException"><paramref name="control"/> is <code>null</code>.</exception>
         public void Show(Control control, Rectangle area)
         {
             Show(control, area, false);
         }

         public void Show(Control control, Rectangle area, bool center)
         {
             if (control == null)
             {
                 throw new ArgumentNullException("control");
             }
             SetOwnerItem(control);
             resizableTop = resizableLeft = false;
             Point location = control.PointToScreen(new Point(area.Left, area.Top + area.Height));
             Rectangle screen = Screen.FromControl(control).WorkingArea;
             if (center)
             {
                 if (location.X + (area.Width + Size.Width) /  > screen.Right)
                 {
                     resizableLeft = true;
                     location.X = screen.Right - Size.Width;
                 }
                 else
                 {
                     resizableLeft = true;
                     location.X = location.X - (Size.Width - area.Width) / ;
                 }
             }
             else
             {
                 if (location.X + Size.Width > (screen.Left + screen.Width))
                 {
                     resizableLeft = true;
                     location.X = (screen.Left + screen.Width) - Size.Width;
                 }
             }

             if (location.Y + Size.Height > (screen.Top + screen.Height))
             {
                 resizableTop = true;
                 location.Y -= Size.Height + area.Height;
             }
             location = control.PointToClient(location);
             Show(control, location, ToolStripDropDownDirection.BelowRight);
         }

         private const int frames = ;
         private const int totalduration = ;
         private const int frameduration = totalduration / frames;
         /// <summary>
         /// Adjusts the size of the owner <see cref="T:System.Windows.Forms.ToolStrip" /> to accommodate the <see cref="T:System.Windows.Forms.ToolStripDropDown" /> if the owner <see cref="T:System.Windows.Forms.ToolStrip" /> is currently displayed, or clears and resets active <see cref="T:System.Windows.Forms.ToolStripDropDown" /> child controls of the <see cref="T:System.Windows.Forms.ToolStrip" /> if the <see cref="T:System.Windows.Forms.ToolStrip" /> is not currently displayed.
         /// </summary>
         /// <param name="visible">true if the owner <see cref="T:System.Windows.Forms.ToolStrip" /> is currently displayed; otherwise, false.</param>
         protected override void SetVisibleCore(bool visible)
         {
             double opacity = Opacity;
             if (visible && fade && focusOnOpen) Opacity = ;
             base.SetVisibleCore(visible);
             if (!visible || !fade || !focusOnOpen) return;
             for (int i = ; i <= frames; i++)
             {
                 if (i > )
                 {
                     System.Threading.Thread.Sleep(frameduration);
                 }
                 Opacity = opacity * (double)i / (double)frames;
             }
             Opacity = opacity;
         }

         private bool resizableTop;
         private bool resizableLeft;

         private void SetOwnerItem(Control control)
         {
             if (control == null)
             {
                 return;
             }
             if (control is PopupForm)
             {
                 PopupForm popupControl = control as PopupForm;
                 ownerPopup = popupControl;
                 ownerPopup.childPopup = this;
                 OwnerItem = popupControl.Items[];
                 return;
             }
             if (control.Parent != null)
             {
                 SetOwnerItem(control.Parent);
             }
         }

         /// <summary>
         /// Raises the <see cref="E:System.Windows.Forms.Control.SizeChanged" /> event.
         /// </summary>
         /// <param name="e">An <see cref="T:System.EventArgs" /> that contains the event data.</param>
         protected override void OnSizeChanged(EventArgs e)
         {
             content.MinimumSize = Size;
             content.MaximumSize = Size;
             content.Size = Size;
             content.Location = Point.Empty;
             base.OnSizeChanged(e);
         }

         /// <summary>
         /// Raises the <see cref="E:System.Windows.Forms.ToolStripDropDown.Opening" /> event.
         /// </summary>
         /// <param name="e">A <see cref="T:System.ComponentModel.CancelEventArgs" /> that contains the event data.</param>
         protected override void OnOpening(CancelEventArgs e)
         {
             if (content.IsDisposed || content.Disposing)
             {
                 e.Cancel = true;
                 return;
             }
             UpdateRegion();
             base.OnOpening(e);
         }

         /// <summary>
         /// Raises the <see cref="E:System.Windows.Forms.ToolStripDropDown.Opened" /> event.
         /// </summary>
         /// <param name="e">An <see cref="T:System.EventArgs" /> that contains the event data.</param>
         protected override void OnOpened(EventArgs e)
         {
             if (ownerPopup != null)
             {
                 ownerPopup._resizable = false;
             }
             if (focusOnOpen)
             {
                 content.Focus();
             }
             _isOpen = true;
             base.OnOpened(e);
         }

         /// <summary>
         /// Raises the <see cref="E:System.Windows.Forms.ToolStripDropDown.Closed"/> event.
         /// </summary>
         /// <param name="e">A <see cref="T:System.Windows.Forms.ToolStripDropDownClosedEventArgs"/> that contains the event data.</param>
         protected override void OnClosed(ToolStripDropDownClosedEventArgs e)
         {
             if (ownerPopup != null)
             {
                 ownerPopup._resizable = true;
             }
             _isOpen = false;
             base.OnClosed(e);
         }

         #endregion

         #region " Resizing Support "

         /// <summary>
         /// Processes Windows messages.
         /// </summary>
         /// <param name="m">The Windows <see cref="T:System.Windows.Forms.Message" /> to process.</param>
         [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
         protected override void WndProc(ref Message m)
         {
             if (InternalProcessResizing(ref m, false))
             {
                 return;
             }
             base.WndProc(ref m);
         }

         /// <summary>
         /// Processes the resizing messages.
         /// </summary>
         /// <param name="m">The message.</param>
         /// <returns>true, if the WndProc method from the base class shouldn't be invoked.</returns>
         [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
         public bool ProcessResizing(ref Message m)
         {
             return InternalProcessResizing(ref m, true);
         }

         [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
         private bool InternalProcessResizing(ref Message m, bool contentControl)
         {
             if (m.Msg == UnsafeMethods.WM_NCACTIVATE && m.WParam != IntPtr.Zero && childPopup != null && childPopup.Visible)
             {
                 childPopup.Hide();
             }
             if (!Resizable)
             {
                 return false;
             }
             if (m.Msg == UnsafeMethods.WM_NCHITTEST)
             {
                 return OnNcHitTest(ref m, contentControl);
             }
             else if (m.Msg == UnsafeMethods.WM_GETMINMAXINFO)
             {
                 return OnGetMinMaxInfo(ref m);
             }
             return false;
         }

         [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
         private bool OnGetMinMaxInfo(ref Message m)
         {
             UnsafeMethods.MINMAXINFO minmax = (UnsafeMethods.MINMAXINFO)Marshal.PtrToStructure(m.LParam, typeof(UnsafeMethods.MINMAXINFO));
             minmax.maxTrackSize = this.MaximumSize;
             minmax.minTrackSize = this.MinimumSize;
             Marshal.StructureToPtr(minmax, m.LParam, false);
             return true;
         }

         private bool OnNcHitTest(ref Message m, bool contentControl)
         {
             int x = UnsafeMethods.LOWORD(m.LParam);
             int y = UnsafeMethods.HIWORD(m.LParam);
             Point clientLocation = PointToClient(new Point(x, y));

             GripBounds gripBouns = new GripBounds(contentControl ? content.ClientRectangle : ClientRectangle);
             IntPtr transparent = new IntPtr(UnsafeMethods.HTTRANSPARENT);

             if (resizableTop)
             {
                 if (resizableLeft && gripBouns.TopLeft.Contains(clientLocation))
                 {
                     m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTTOPLEFT;
                     return true;
                 }
                 if (!resizableLeft && gripBouns.TopRight.Contains(clientLocation))
                 {
                     m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTTOPRIGHT;
                     return true;
                 }
                 if (gripBouns.Top.Contains(clientLocation))
                 {
                     m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTTOP;
                     return true;
                 }
             }
             else
             {
                 if (resizableLeft && gripBouns.BottomLeft.Contains(clientLocation))
                 {
                     m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTBOTTOMLEFT;
                     return true;
                 }
                 if (!resizableLeft && gripBouns.BottomRight.Contains(clientLocation))
                 {
                     m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTBOTTOMRIGHT;
                     return true;
                 }
                 if (gripBouns.Bottom.Contains(clientLocation))
                 {
                     m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTBOTTOM;
                     return true;
                 }
             }
             if (resizableLeft && gripBouns.Left.Contains(clientLocation))
             {
                 m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTLEFT;
                 return true;
             }
             if (!resizableLeft && gripBouns.Right.Contains(clientLocation))
             {
                 m.Result = contentControl ? transparent : (IntPtr)UnsafeMethods.HTRIGHT;
                 return true;
             }
             return false;
         }

         private VS.VisualStyleRenderer sizeGripRenderer;
         /// <summary>
         /// Paints the sizing grip.
         /// </summary>
         /// <param name="e">The <see cref="System.Windows.Forms.PaintEventArgs" /> instance containing the event data.</param>
         public void PaintSizeGrip(PaintEventArgs e)
         {
             if (e == null || e.Graphics == null || !resizable)
             {
                 return;
             }
             Size clientSize = content.ClientSize;
             using (Bitmap gripImage = new Bitmap(0x10, 0x10))
             {
                 using (Graphics g = Graphics.FromImage(gripImage))
                 {
                     if (Application.RenderWithVisualStyles)
                     {
                         if (this.sizeGripRenderer == null)
                         {
                             this.sizeGripRenderer = new VS.VisualStyleRenderer(VS.VisualStyleElement.Status.Gripper.Normal);
                         }
                         this.sizeGripRenderer.DrawBackground(g, new Rectangle(, , 0x10, 0x10));
                     }
                     else
                     {
                         ControlPaint.DrawSizeGrip(g, content.BackColor, , , 0x10, 0x10);
                     }
                 }
                 GraphicsState gs = e.Graphics.Save();
                 e.Graphics.ResetTransform();
                 if (resizableTop)
                 {
                     if (resizableLeft)
                     {
                         e.Graphics.RotateTransform();
                         e.Graphics.TranslateTransform(-clientSize.Width, -clientSize.Height);
                     }
                     else
                     {
                         e.Graphics.ScaleTransform(, -);
                         e.Graphics.TranslateTransform(, -clientSize.Height);
                     }
                 }
                 else if (resizableLeft)
                 {
                     e.Graphics.ScaleTransform(-, );
                     e.Graphics.TranslateTransform(-clientSize.Width, );
                 }
                 e.Graphics.DrawImage(gripImage, clientSize.Width - 0x10, clientSize.Height - 0x10 + , 0x10, 0x10);
                 e.Graphics.Restore(gs);
             }
         }

         #endregion
     }
 }

然后新建一个自定义控件，代码如下

 ：
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Drawing;
 using System.Data;
 using System.Linq;
 using System.Text;
 using System.Windows.Forms;
 using System.Collections;
 using System.Reflection;
 using Newtonsoft.Json.Linq;

 namespace Controls
 {

     /// <summary>
     /// 功能描述:自定义多选下拉框
     /// 作　　者:huangzh
     /// 创建日期:2016-01-04 11:57:13
     /// 任务编号:
     /// </summary>
     public class ComboBoxEx : ComboBox
     {
         PopupForm frmhost;
         TreeView lst = new TreeView();
         /// <summary>
         /// 功能描述:构造方法
         /// 作　　者:huangzh
         /// 创建日期:2016-01-04 11:57:27
         /// 任务编号:
         /// </summary>
         public ComboBoxEx()
         {
             this.DrawMode = DrawMode.OwnerDrawFixed;//只有设置这个属性为OwnerDrawFixed才可能让重画起作用   

             lst.Width = ListWidth ==  ? this.Width : ListWidth;
             lst.Height = ListHeight ==  ?  : ListHeight;
             lst.CheckBoxes = true;
             lst.ShowLines = false;
             lst.ShowPlusMinus = false;
             lst.ShowRootLines = false;
             lst.KeyUp += new KeyEventHandler(lst_KeyUp);
             lst.AfterCheck += new TreeViewEventHandler(lst_AfterCheck);
             this.DropDownHeight = ;
             frmhost = new PopupForm(lst);
             //frmhost.Closed += new ToolStripDropDownClosedEventHandler(frmhost_Closed);
             //frmhost.Opened += new EventHandler(frmhost_Opened);
         }

         void lst_KeyUp(object sender, KeyEventArgs e)
         {
             OnKeyUp(e);
         }

         void lst_AfterCheck(object sender, TreeViewEventArgs e)
         {
             if (e.Node.Checked)
             {
                 if (Text != "")
                 {
                     Text += ",";
                 }
                 Text += e.Node.Tag.ToString();
             }
             else
             {
                 string strValue = e.Node.Tag.ToString().Trim();
                 if (Text != "")
                 {
                     List<string> strs = Text.Split(',').ToList();
                     strs.Remove("");
                     if (strs.Contains(strValue))
                     {
                         strs.Remove(strValue);
                         Text = string.Join(",", strs);
                     }
                 }
             }
         }

         void frmhost_Opened(object sender, EventArgs e)
         {

         }

         void frmhost_Closed(object sender, ToolStripDropDownClosedEventArgs e)
         {

         }

         #region Property
         /// <summary>
         /// 选中项
         /// </summary>
         [Description("选定项的值"), Category("Data")]
         public List<TreeNode> SelectedItems
         {
             get
             {
                 List<TreeNode> lsttn = new List<TreeNode>();
                 foreach (TreeNode tn in lst.Nodes)
                 {
                     if (tn.Checked)
                     {
                         lsttn.Add(tn);
                     }
                 }
                 return lsttn;
             }
         }

         /// <summary>
         /// 数据源
         /// </summary>
         [Description("数据源"), Category("Data")]
         public new object DataSource
         {
             get;
             set;
         }
         /// <summary>
         /// 显示字段
         /// </summary>
         [Description("显示字段"), Category("Data")]
         public string DisplayFiled
         {
             get;
             set;
         }
         /// <summary>
         /// 值字段
         /// </summary>
         [Description("值字段"), Category("Data")]
         public string ValueFiled
         {
             get;
             set;
         }
         /// <summary>
         /// 列表高度
         /// </summary>
         [Description("列表高度"), Category("Data")]
         public int ListHeight
         {
             get;
             set;
         }

         /// <summary>
         /// 列表宽度
         /// </summary>
         [Description("列表宽度"), Category("Data")]
         public int ListWidth
         {
             get;
             set;
         }
         #endregion

         /// <summary>
         /// 功能描述:绑定数据
         /// 作　　者:huangzh
         /// 创建日期:2016-01-04 10:38:51
         /// 任务编号:
         /// </summary>
         public void DataBind()
         {
             this.BeginUpdate();
             if (DataSource != null)
             {
                 if (DataSource is IDataReader)
                 {
                     DataTable dataTable = new DataTable();
                     dataTable.Load(DataSource as IDataReader);

                     DataBindToDataTable(dataTable);
                 }
                 else if (DataSource is DataView || DataSource is DataSet || DataSource is DataTable)
                 {
                     DataTable dataTable = null;

                     if (DataSource is DataView)
                     {
                         dataTable = ((DataView)DataSource).ToTable();
                     }
                     else if (DataSource is DataSet)
                     {
                         dataTable = ((DataSet)DataSource).Tables[];
                     }
                     else
                     {
                         dataTable = ((DataTable)DataSource);
                     }

                     DataBindToDataTable(dataTable);
                 }
                 else if (DataSource is IEnumerable)
                 {
                     DataBindToEnumerable((IEnumerable)DataSource);
                 }
                 else
                 {
                     throw new Exception("DataSource doesn't support data type: " + DataSource.GetType().ToString());
                 }
             }
             else
             {
                 lst.Nodes.Clear();
             }

             this.EndUpdate();
         }

         /// <summary>
         /// 功能描述:绑定Table数据
         /// 作　　者:huangzh
         /// 创建日期:2016-01-04 10:47:27
         /// 任务编号:
         /// </summary>
         /// <param name="dt">dt</param>
         private void DataBindToDataTable(DataTable dt)
         {
             foreach (DataRow dr in dt.Rows)
             {
                 TreeNode tn = new TreeNode();
                 if (!string.IsNullOrEmpty(DisplayFiled) && !string.IsNullOrEmpty(ValueFiled))
                 {
                     tn.Text = dr[DisplayFiled].ToString();
                     tn.Tag = dr[ValueFiled].ToString();
                 }
                 else if (string.IsNullOrEmpty(ValueFiled))
                 {
                     tn.Text = dr[DisplayFiled].ToString();
                     tn.Tag = dr[DisplayFiled].ToString();
                 }
                 else if (string.IsNullOrEmpty(DisplayFiled))
                 {
                     tn.Text = dr[ValueFiled].ToString();
                     tn.Tag = dr[ValueFiled].ToString();
                 }
                 else
                 {
                     throw new Exception("ValueFiled和DisplayFiled至少保证有一项有值");
                 }
                 tn.ToolTipText = tn.Text;

                 tn.Checked = false;
                 lst.Nodes.Add(tn);
             }
         }

         /// <summary>
         /// 绑定到可枚举类型
         /// </summary>
         /// <param name="enumerable">可枚举类型</param>
         private void DataBindToEnumerable(IEnumerable enumerable)
         {
             IEnumerator enumerator = enumerable.GetEnumerator();
             while (enumerator.MoveNext())
             {
                 object currentObject = enumerator.Current;
                 lst.Nodes.Add(CreateListItem(currentObject));
             }
         }

         /// <summary>
         /// 功能描述:获取一个CheckBox
         /// 作　　者:huangzh
         /// 创建日期:2016-01-04 10:53:12
         /// 任务编号:
         /// </summary>
         /// <param name="obj">obj</param>
         /// <returns>返回值</returns>
         private TreeNode CreateListItem(Object obj)
         {
             TreeNode item = new TreeNode();

             if (obj is string)
             {
                 item.Text = obj.ToString();
                 item.Tag = obj.ToString();
             }
             else
             {
                 if (DisplayFiled != "")
                 {
                     item.Text = GetPropertyValue(obj, DisplayFiled);
                 }
                 else
                 {
                     item.Text = obj.ToString();
                 }

                 if (ValueFiled != "")
                 {
                     item.Tag = GetPropertyValue(obj, ValueFiled);
                 }
                 else
                 {
                     item.Tag = obj.ToString();
                 }
             }
             item.ToolTipText = item.Text;
             return item;
         }

         /// <summary>
         /// 取得属性值
         /// </summary>
         /// <param name="obj"></param>
         /// <param name="propertyName"></param>
         private string GetPropertyValue(object obj, string propertyName)
         {
             object result = null;

             result = ObjectUtil.GetPropertyValue(obj, propertyName);
             return result == null ? String.Empty : result.ToString();
         }

         #region override

         /// <summary>
         /// 功能描述:OnKeyUp
         /// 作　　者:huangzh
         /// 创建日期:2016-01-04 11:58:33
         /// 任务编号:
         /// </summary>
         /// <param name="e">e</param>
         protected override void OnKeyUp(KeyEventArgs e)
         {
             base.OnKeyDown(e);
             bool Pressed = (e.Control && ((e.KeyData & Keys.A) == Keys.A));
             if (Pressed)
             {
                 this.Text = "";
                 for (int i = ; i < lst.Nodes.Count; i++)
                 {
                     lst.Nodes[i].Checked = true;
                 }
             }
         }

         /// <summary>
         /// 功能描述:OnDropDown
         /// 作　　者:huangzh
         /// 创建日期:2016-01-04 11:58:53
         /// 任务编号:
         /// </summary>
         /// <param name="e">e</param>
         protected override void OnDropDown(EventArgs e)
         {
             this.DroppedDown = false;
             string strValue = this.Text;
             if (!string.IsNullOrEmpty(strValue))
             {
                 List<string> lstvalues = strValue.Split(',').ToList<string>();
                 foreach (TreeNode tn in lst.Nodes)
                 {
                     if (tn.Checked && !lstvalues.Contains(tn.Tag.ToString()) && !string.IsNullOrEmpty(tn.Tag.ToString().Trim()))
                     {
                         tn.Checked = false;
                     }
                     else if (!tn.Checked && lstvalues.Contains(tn.Tag.ToString()) && !string.IsNullOrEmpty(tn.Tag.ToString().Trim()))
                     {
                         tn.Checked = true;
                     }
                 }
             }
             else
             {
                 foreach (TreeNode tn in lst.Nodes)
                 {
                     tn.Checked = false;
                 }
             }
             frmhost.Show(this);
         }
         #endregion
     }

     /// <summary>
     /// 对象帮助类
     /// </summary>
     public class ObjectUtil
     {
         /// <summary>
         /// 获取对象的属性值
         /// </summary>
         /// <param name="obj">可能是DataRowView或一个对象</param>
         /// <param name="propertyName">属性名</param>
         /// <returns>属性值</returns>
         public static object GetPropertyValue(object obj, string propertyName)
         {
             object result = null;

             try
             {
                 if (obj is DataRow)
                 {
                     result = (obj as DataRow)[propertyName];
                 }
                 else if (obj is DataRowView)
                 {
                     result = (obj as DataRowView)[propertyName];
                 }
                 else if (obj is JObject)
                 {
                     result = (obj as JObject).Value<JValue>(propertyName).Value; //.getValue(propertyName);
                 }
                 else
                 {
                     result = GetPropertyValueFormObject(obj, propertyName);
                 }
             }
             catch (Exception)
             {
                 // 找不到此属性
             }

             return result;
         }

         /// <summary>
         /// 获取对象的属性值
         /// </summary>
         /// <param name="obj">对象</param>
         /// <param name="propertyName">属性名（"Color"、"BodyStyle"或者"Info.UserName"）</param>
         /// <returns>属性值</returns>
         private static object GetPropertyValueFormObject(object obj, string propertyName)
         {
             object rowObj = obj;
             object result = null;

             if (propertyName.IndexOf(".") > )
             {
                 string[] properties = propertyName.Split('.');
                 object tmpObj = rowObj;

                 for (int i = ; i < properties.Length; i++)
                 {
                     PropertyInfo property = tmpObj.GetType().GetProperty(properties[i], BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
                     if (property != null)
                     {
                         tmpObj = property.GetValue(tmpObj, null);
                     }
                 }

                 result = tmpObj;
             }
             else
             {
                 PropertyInfo property = rowObj.GetType().GetProperty(propertyName, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
                 if (property != null)
                 {
                     result = property.GetValue(rowObj, null);
                 }
             }

             return result;
         }
     }
 }

然后就是使用了，直接拖一个到界面上，然后设置值就可以了

ListHeight，ListWidth 这两个属性一定要修改下的哦

然后就是绑定数据源

  var varSourceFrom = from p in lstEnumEnitty
                                    where p.Type == "source"
                                    select p;
                cboSourceFromType.DataSource = varSourceFrom;
                cboSourceFromType.DisplayFiled = "Name";
                cboSourceFromType.ValueFiled = "Code";
                cboSourceFromType.DataBind();

效果就是这样的了

需要引用的一个DLL去我的上一个文章里面下载吧