Custom textbox control

Question

Is it possible to create a textbox in Visual Studio like this:

if you are using winforms you can add water mark (username ) in your case to the textbox... — Glory Raj, Feb 12 '12 at 09:32
Does the text disappear once you click on the box like SO's search box? — Ash Burlaczenko, Feb 12 '12 at 09:48

score 17 · Answer 1 · answered Feb 12 '12 at 10:24

Actually. A better solution will be simply use the Paint event of the text box to draw the string.

Here's the code:

class CueTextBox : TextBox
{
    public event EventHandler CueTextChanged;
    private string _cueText;

    public string CueText
    {
        get { return _cueText; }
        set
        {
            value = value ?? string.Empty;
            if (value != _cueText)
            {
                _cueText = value;
                OnCueTextChanged(EventArgs.Empty);
            }
        }
    }

    public CueTextBox()
        : base()
    {
        _cueText = string.Empty;
    }

    protected virtual void OnCueTextChanged(EventArgs e)
    {
        this.Invalidate(true);
        if (this.CueTextChanged != null)
            this.CueTextChanged(this, e);
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        if (string.IsNullOrEmpty(this.Text.Trim()) && !string.IsNullOrEmpty(this.CueText) && !this.Focused)
        {
            Point startingPoint = new Point(0, 0);
            StringFormat format = new StringFormat();
            Font font = new Font(this.Font.FontFamily.Name, this.Font.Size, FontStyle.Italic);
            if (this.RightToLeft == RightToLeft.Yes)
            {
                format.LineAlignment = StringAlignment.Far;
                format.FormatFlags = StringFormatFlags.DirectionRightToLeft;
            }
            e.Graphics.DrawString(CueText, font, Brushes.Gray, this.ClientRectangle, format);
        }
    }

    const int WM_PAINT = 0x000F;
    protected override void WndProc(ref Message m)
    {
        base.WndProc(ref m);
        if (m.Msg == WM_PAINT)
        {
            this.OnPaint(new PaintEventArgs(Graphics.FromHwnd(m.HWnd), this.ClientRectangle));
        }
    }
}

Now, all you need is the set the 'CueText' property to the initial value you want and you're done!

This way you don't modify the 'Text' property of the textbox, which could lead to unexpected results. On my solution the text is only painted over the textbox area, and you can use the Text property without any worries — Nissim, Jun 26 '12 at 08:27
I like your method, although you should always call the `Dispose` method to release the Graphics and related resources created by the `FromHwnd` method. So I suggest the code `using (Graphics g = Graphics.FromHwnd(m.HWnd)) { this.OnPaint(new PaintEventArgs(g, this.ClientRectangle)); }` — Ricardo González, Apr 26 '18 at 12:18

score 3 · Accepted Answer · answered Feb 12 '12 at 10:57

You would just need to handle three TextBox events, in the Designer set the text of the TextBox to "username" and make it Font Italics then set TextBox BackColor to LightYellow,the rest is handled by Event handlers...

     private void textBox1_TextChanged(object sender, EventArgs e)
    {
        if (textBox1.Text == "")
            ChangeTextBoxtoWatermark();
    }

    private void textBox1_MouseEnter(object sender, EventArgs e)
    {
        if (textBox1.Text == "username")
        {
            textBox1.Text = "";
            textBox1.Font = new Font(this.Font, FontStyle.Regular);
            textBox1.BackColor = Color.White;
        }
    }

    private void textBox1_MouseLeave(object sender, EventArgs e)
    {
        if (textBox1.Text == "")
            ChangeTextBoxtoWatermark();
    }

    private void ChangeTextBoxtoWatermark()
    {
        textBox1.Font = new Font(this.Font, FontStyle.Italic);
        textBox1.BackColor = Color.LightYellow;
        textBox1.Text = "username";
    }

I have checked it and it works fine :)

You can refractor the code like TextBoxToOriginal() – DayTimeCoder Feb 12 '12 at 10:59 — DayTimeCoder, Feb 12 '12 at 10:59

Custom textbox control

2 Answers2

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