c#winform - textbox控件添加背景图片

===========================从textbox类继承处理绘制背景消息====================
    class MyTextBox : TextBox
    {
        const int WM_ERASEBKGND = 0x0014;

        private Image backImage;

        [DisplayName("背景图片。")]
        public Image BackImage
        {
            get { return backImage; }
            set { backImage = value; }
        }

        protected void OnEraseBkgnd(Graphics gs)
        {
            gs.FillRectangle(Brushes.White, 0, 0, this.Width, this.Height); //填充为白色，防止图片太小出现重影
            if (backImage != null) gs.DrawImage(backImage, 0, 0); //绘制背景。
            gs.Dispose();
        }

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_ERASEBKGND) //绘制背景
            {
                OnEraseBkgnd(Graphics.FromHdc(m.WParam));
                m.Result = (IntPtr)1;
            }
            base.WndProc(ref m);
        }
    }

==================窗口类里设置控件的字体颜色等=============================

        const int WM_CTLCOLOREDIT = 0x0133;
        const int TRANSPARENT = 0x1;
        const int NULL_BRUSH = 0x5;

        [DllImport("gdi32")]
        static extern int SetBkMode(IntPtr hdc, int bkMode);
        [DllImport("gdi32")]
        static extern int SetTextColor(IntPtr hdc, int color);
        [DllImport("gdi32")]
        static extern IntPtr GetStockObject(int fnobject);

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_CTLCOLOREDIT && m.LParam == myTextBox1.Handle)//类型为EDIT(TextBox)
            {
                SetBkMode(m.WParam, TRANSPARENT);//设置背景透明
                SetTextColor(m.WParam,0xFF);     //字体颜色为红色
                m.Result = GetStockObject(NULL_BRUSH);
                return;
            }
            else base.WndProc(ref m);
        }