Winform

代码

 public class TextBoxEx : TextBox{public String PlaceHolderStr { get; set; }protected override void WndProc(ref Message m){base.WndProc(ref m);if (m.Msg == 0xF || m.Msg == 0x133){WmPaint(ref m);}}private void WmPaint(ref Message m){Graphics g = Graphics.FromHwnd(base.Handle);if (!String.IsNullOrEmpty(this.PlaceHolderStr) && string.IsNullOrEmpty(this.Text))g.DrawString(this.PlaceHolderStr, this.Font, new SolidBrush(Color.LightGray), 0, 0);}}

效果图

Winform

代码

 public class TextBoxEx : TextBox{public String PlaceHolderStr { get; set; }protected override void WndProc(ref Message m){base.WndProc(ref m);if (m.Msg == 0xF || m.Msg == 0x133){WmPaint(ref m);}}private void WmPaint(ref Message m){Graphics g = Graphics.FromHwnd(base.Handle);if (!String.IsNullOrEmpty(this.PlaceHolderStr) && string.IsNullOrEmpty(this.Text))g.DrawString(this.PlaceHolderStr, this.Font, new SolidBrush(Color.LightGray), 0, 0);}}

效果图