(C#)Winform修改DateTimePicker控件的背景色和邊框色

(C#)Winform修改DateTimePicker控件的背景色Winform中日期控件DateTimePicker默認是不能修改背景色和邊框色的，如果想要改變它的背景色和邊框色

那也是有辦法的，只需要繼承DateTimePicker做一個自定義控件，再重寫WndProc方法。此外還要重寫屬性，這樣就可以在外部修改它的顏色了。 自定義控件的完整代碼如下：

 public class UCDateTime : DateTimePicker
    { 
[DllImport("user32.dll", EntryPoint = "SendMessageA")]
        private static extern int SendMessage(IntPtr hwnd, int wMsg, IntPtr wParam, object lParam);

        [DllImport("user32")]
        private static extern IntPtr GetWindowDC(IntPtr hWnd);

        [DllImport("user32")]
        private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);
        const int WM_ERASEBKGND = 0x14;
        const int WM_NC_PAINT = 0x85;
        const int WM_PAINT = 0xF;
        const int WM_PRINTCLIENT = 0x318;

        //邊框顏色
        private Pen BorderPen = new Pen(SystemColors.ControlDark, 2);

        /// <summary>
        /// 定義背景色私有變量
        /// </summary>
        private Color _backColor = Color.White;
        /// <summary>
        /// 定義背景色屬性
        /// </summary>
        public override Color BackColor
        {
            get
            {
                return _backColor;
            }
            set
            {
                _backColor = value;
            }
        }
        
        protected override void WndProc(ref System.Windows.Forms.Message m)
        {
            IntPtr hDC = IntPtr.Zero;
            Graphics gdc = null;
            switch (m.Msg)
            {
                //畫背景色
                case WM_ERASEBKGND:
                    gdc = Graphics.FromHdc(m.WParam);
                    gdc.FillRectangle(new SolidBrush(_backColor), new Rectangle(0, 0, this.Width, this.Height));
                    gdc.Dispose();
                    break;
                case WM_NC_PAINT:
                    hDC = GetWindowDC(m.HWnd);
                    gdc = Graphics.FromHdc(hDC);
                    SendMessage(this.Handle, WM_ERASEBKGND, hDC, 0);
                    SendPrintClientMsg();
                    SendMessage(this.Handle, WM_PAINT, IntPtr.Zero, 0);
                    m.Result = (IntPtr)1;    // indicate msg has been processed
                    ReleaseDC(m.HWnd, hDC);
                    gdc.Dispose();
                    break;
                //畫邊框
                case WM_PAINT:
                    base.WndProc(ref m);
                    hDC = GetWindowDC(m.HWnd);
                    gdc = Graphics.FromHdc(hDC);
                    OverrideControlBorder(gdc);
                    ReleaseDC(m.HWnd, hDC);
                    gdc.Dispose();
                    break;
                default:
                    base.WndProc(ref m);
                    break;
            }
        }

        private void SendPrintClientMsg()
        {
            // We send this message for the control to redraw the client area
            Graphics gClient = this.CreateGraphics();
            IntPtr ptrClientDC = gClient.GetHdc();
            SendMessage(this.Handle, WM_PRINTCLIENT, ptrClientDC, 0);
            gClient.ReleaseHdc(ptrClientDC);
            gClient.Dispose();
        }

        private void OverrideControlBorder(Graphics g)
        {
           g.DrawRectangle(BorderPen, new Rectangle(0, 0, this.Width, this.Height));
        }
}