Winform透かしTextBox(ほぼ完璧)

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(" "), Description(" ")]

    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);

    //}

}

新しい方法(回転):
 public partial class PromptTextBox : TextBox    {        private string promptString = string.Empty;        private bool IsEmpty = true;        public PromptTextBox()        {            InitializeComponent();        }        public PromptTextBox(string prompt)        {            InitializeComponent();            PromptString = prompt;        }       /**/       ///

       ///Prompt Text       ///

        public string PromptString        {            get { return promptString; }            set { promptString = value; }        }        protected override void OnEnter(EventArgs e)        {            if (IsEmpty) { Clear(); }        }        protected override void OnLeave(EventArgs e)        {            if (Text == string.Empty)            {                Text = PromptString;                IsEmpty = true;            }            else { IsEmpty = false; }        }        public override string Text        {            get            {                if (IsEmpty) { return string.Empty; }                else { return base.Text; }            }            set            {                if (value == string.Empty)                {                    base.Text = PromptString;                    IsEmpty = true;                }                else                {                    IsEmpty = (value == PromptString);                    base.Text = value;                }            }        }        protected override void OnCreateControl()        {            if (Text == string.Empty)            {                Text = PromptString;                IsEmpty = true;            }            else { IsEmpty = false; }        }    }