validate textbox with only decimal numbers (positive and negative)

Question

I have a textbox in C# where the user can enter only decimal numbers (negative and positive).

I don't want to use MaskedText Box, I would rather implement this using the keypress event to validate inputs.

How can I achieve this?

Thanks,

*********EDIT*********++

 private void mytextbox_KeyPress(object sender, KeyPressEventArgs e)
        {
   if (((e.KeyChar < 48 || e.KeyChar > 57) && e.KeyChar != 8 && e.KeyChar != '.' &&e.KeyChar!='-'))
            {
                e.Handled = true;
            }

            if (e.KeyChar == '.')
            {
                if ((sender as TextBox).Text.IndexOf(e.KeyChar) != -1)
                    e.Handled = true;
            }

          if (e.KeyChar=='-' && (sender as TextBox).SelectionStart > 0)
          {
                  e.Handled = true;
          }
}

Have you tried this? http://stackoverflow.com/questions/7259128/limit-numbers-after-decimal-on-key-press-event — abramlimpin, May 15 '14 at 01:17

score 0 · Answer 1 · edited May 23 '17 at 11:57

TryParse for the various numeric types will tell you if the input is valid. For example, if you want to use a double:

private void OnKeyPress(...)
{
   double parsedValue = 0;
   if (double.TryParse(MyTextBox.Text, out parsedValue)
   {
       //Valid number entered, value in parsedValue
   }
   else
   {
       //Invalid number entered
   }
}

This answer has a lot of other ways to accompish this: How do I make a textbox that only accepts numbers?

validate textbox with only decimal numbers (positive and negative)

1 Answers1