Question

I’m trying to mimic the web functionality of having a label over a textbox that shows the type of value the textbox should contain. I can add the events individually but I’m wondering if there is a way to add ‘Behavior’ to a set of controls.

Please see example code:

private void labelFirstName_Click(object sender, EventArgs e)
{
    HideLabelFocusTextBox(labelFirstName, textBoxFirstName);
}

private void HideLabelFocusTextBox(Label LabelToHide, TextBox TextBoxToShow)
{
    LabelToHide.Visible = false;
    TextBoxToShow.Focus();
}

private void textBoxFirstName_Leave(object sender, EventArgs e)
{
    if (String.IsNullOrEmpty(textBoxFirstName.Text))
        labelFirstName.Visible = true;
}

private void textBoxFirstName_Enter(object sender, EventArgs e)
{
    labelFirstName.Visible = false;
}

Answer 1

You could subclass the text box control (write your own that inherits a textbox)

Btw, i have thought about this and i would take another approach:

i would override the text box’s paint handler and when the textbox contains no information, draw an info string into it.

Something like:

using System;
using System.Windows.Forms;
using System.Drawing;

class MyTextBox : TextBox
{
    public MyTextBox()
    {
        SetStyle(ControlStyles.UserPaint, true);
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        if (string.IsNullOrEmpty(this.Text))
        {
            e.Graphics.DrawString("My info string...", this.Font, System.Drawing.Brushes.Gray, new System.Drawing.PointF(0, 0));
        }
        else
        {
            e.Graphics.DrawString(Text, this.Font, new SolidBrush(this.ForeColor) , new System.Drawing.PointF(0, 0));
        }
    }

    protected override void OnTextChanged(EventArgs e)
    {
        Invalidate();
        base.OnTextChanged(e);
    }
}