Validate number INTEGER on text boxes IN windows forms issue

Question

i have textbox on a windows form and i want to be insert only numbers in this textbox.i use the following c# code for that

private void ChildAge_TextChanged(object sender, EventArgs e)
{
    int i;
    if (!int.TryParse(ChildAge.Text, out i))
    {
        MessageBox.Show("Plaese enter a valid Age");
    }    
}

it is working, but the problem is that , after showing the Message, when i Backspace the content and text box become null, on that situation also this message box shows again.

I assume you mean that ChildAge.Text becomes null? Not the actual ChildAge? — Arran
– Arran, Commented Mar 14, 2014 at 9:19
yes. first time no problem , only when click backspace and all content remove from text box again this msgbox shows — neel
– neel, Commented Mar 14, 2014 at 9:22
Do a test like this if(!string.isNullEmpty(ChildAge.Text)) { if (!int.TryParse(ChildAge.Text, out i)) { MessageBox.Show("Plaese enter a valid Age"); } } — Mehbube Arman
– Mehbube Arman, Commented Mar 14, 2014 at 9:23
erm, (!string.IsNullOrWhitespace(ChildAge.Text) && !int.TryParse(ChildAge.Text, out i)) — Jodrell
– Jodrell, Commented Mar 14, 2014 at 9:25
or instead override OnKeyPress and cancel any presses that don't pass char.IsDigit. — Jodrell
– Jodrell, Commented Mar 14, 2014 at 9:27

Mehbube Arman · Accepted Answer · 2014-03-14 10:02:08Z

5

Do a little test like bellow:

int i = 0;
if(!string.IsNullOrEmpty(ChildAge.Text) && 
     !int.TryParse(ChildAge.Text, out i)
  )
{
    MessageBox.Show("Enter Valid Age");
}

edited Mar 14, 2014 at 10:02

answered Mar 14, 2014 at 9:27

Mehbube Arman

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1 Comment

Jodrell Over a year ago

could use && to save indentation

Kishore Anumala · Accepted Answer · 2014-03-14 09:50:36Z

0

Try Using Below. This works better.

  bool m_BackPressed = false;
    private void ChildAge_TextChanged(object sender, EventArgs e)
    {
        int i;
        if (!m_BackPressed)            
        {
            if (!int.TryParse(ChildAge.Text, out i))
            {
                MessageBox.Show("Plaese enter a valid Age");
            } 
        }


    }

    private void ChildAge_KeyPress(object sender, KeyPressEventArgs e)
    {

        m_BackPressed = (e.KeyChar.Equals((char)Keys.Back)) ? true : false;
    }

answered Mar 14, 2014 at 9:50

Kishore Anumala

1

1 Comment

Kishore Anumala Over a year ago

yes. But what if user enters multiple characters and then start pressing backspace to delete all characters in textbox?

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