Question

Example: after I swiped the credit card the value will be displayed on textBox1 and what I want to happen is that the focus will be automatically go to textBox2.

What Textbox event should I use for this?

Thanks!

Here is the screenshot I use the textchange event and im using a testcard

Answer 1

You should listen to the Text Changed event, but only focus the next textbox if you got all the information you need on the current one (i.e all digits were entered)

private void TxtBox1TextChanged(object sender, EventArgs e)
{
    if (txtBox1.Text.Length == LENGTH_OF_CREDIT_CARD_NUMBER)
    {
        txtBox2.Focus();
    }
}

I suggest setting a max length to txtBox1 and then checking:

if (txtBox1.Text.Length == txtBox1.MaxLength)