(转)：Winform 水印TextBox(近乎完美)

public partial class WaterTextBox : TextBox
{
    private readonly Label lblwaterText = new Label();

    public WaterTextBox()
    {
        InitializeComponent();
        lblwaterText.BorderStyle = BorderStyle.None;
        lblwaterText.Enabled = false;
        lblwaterText.BackColor = Color.White;
        lblwaterText.AutoSize = false;
        lblwaterText.Top = 1;
        lblwaterText.Left = 2;
        lblwaterText.FlatStyle = FlatStyle.System;
        Controls.Add(lblwaterText);
    }

    [Category("扩展属性"), Description("显示的提示信息")]
    public string WaterText
    {
        get { return lblwaterText.Text; }
        set { lblwaterText.Text = value; }
    }

    public override string Text
    {
        set
        {
            lblwaterText.Visible = value == string.Empty;
            base.Text = value;
        }
        get
        {
            return base.Text;
        }
    }

    protected override void OnSizeChanged(EventArgs e)
    {
        if (Multiline && (ScrollBars == ScrollBars.Vertical || ScrollBars == ScrollBars.Both))
            lblwaterText.Width = Width - 20;
        else
            lblwaterText.Width = Width;
        lblwaterText.Height = Height - 2;
        base.OnSizeChanged(e);
    }

    protected override void OnTextChanged(EventArgs e)
    {
        lblwaterText.Visible = base.Text == string.Empty;
        base.OnTextChanged(e);
    }

    protected override void OnMouseDown(MouseEventArgs e)
    {
        lblwaterText.Visible = false;
        base.OnMouseDown(e);
    }

    protected override void OnMouseLeave(EventArgs e)
    {
        lblwaterText.Visible = base.Text == string.Empty;
        base.OnMouseLeave(e);
    }

    //protected override void OnEnter(EventArgs e)
    //{
    //    lblwaterText.Visible = false;
    //    base.OnEnter(e);
    //}

    //protected override void OnLeave(EventArgs e)
    //{
    //    if (string.IsNullOrEmpty(base.Text))
    //        lblwaterText.Visible = true;
    //    base.OnLeave(e);
    //}
}