want to interrupt first char form zero

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I am working on a textbox. I used a keydown event for handling pressed key. Now I need to do in my keydown event to interrupt the first char from 0. Suppose in my textbox I pressed 779. Now if I press 0 before 779, then I want to disable 0 that means e.handled=true. I could solved it if I will know length position of press key in that time. My code will like the following:

C#

private void txtBianry_KeyDown(object sender, KeyEventArgs e)
{
    if (pressed key is of first length and 0 from full of text)
         e.Handled = true;

    // continue...
}

How can I solve this?
Thanks in advance.

Posted 12-Jan-13 5:18am

Member 8454009

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OriginalGriff 12-Jan-13 11:38am

Answer updated

2 solutions

Solution 2

I'd use a NumericUpDown. And There is at least one article on here showing how to do this. Failing that, can't you just check the Length of the existing value?

Posted 12-Jan-13 5:38am

PIEBALDconsult

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OriginalGriff · Accepted Answer · 2013-01-12T05:32:00

Look at the TextBox.SelectionStart property - it gives the current caret position. If it is zero, and the SelectionLength is zero, the cursor is at the start and no text is selected.

[edit]
BTW: You don't want this in KeyDown - you want it in KeyPress:

C#

private void myTextBox_KeyPress(object sender, KeyPressEventArgs e)
    {
    TextBox tb = sender as TextBox;
    if (tb != null)
        {
        if (tb.SelectionStart == 0 && tb.SelectionLength == 0 && e.KeyChar == '0')
            {
            e.Handled = true;
            }
        }
    }

[/edit]