Masking a textbox for Numbers only buit wont accept BackSpace

Question

Hello, I have a textbox that I would like for only numbers. But if I hit the wrong number, I cant backspace to correct it. How can I allow backspaces to work. Thanks

    private void amount_PaidTextBox_KeyPress(object sender, KeyPressEventArgs e)
    {
        if (Char.IsNumber(e.KeyChar) != true)
        {
            e.Handled = true;
        }
    }

Answer 1

You could add a check to allow control characters as well:

if (Char.IsControl(e.KeyChar) != true && Char.IsNumber(e.KeyChar) != true)
{
    e.Handled = true;
}

Update: in response to person-b's comment on the code s/he suggests the following style (which is also how I would personally write this):

if (!Char.IsControl(e.KeyChar) && !Char.IsNumber(e.KeyChar))
{
    e.Handled = true;
}

Answer 2

private void amount_PaidTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
     if (!Char.IsNumber(e.KeyChar) && e.KeyCode != Keys.Back)
          e.Handled = True;
}

Answer 3

A slightly cleaner format of the above:

 private void amount_PaidTextBox_KeyPress(object sender, KeyPressEventArgs e)
 {
   e.Handled = !(Char.IsNumber(e.KeyChar) || (e.KeyChar==Keys.Back));
 }

Answer 4

You can also override the TextChanged-event:

private void textBox1_TextChanged(object sender, EventArgs e)
{
    string text = (sender as TextBox).Text;

    StringBuilder builder = new StringBuilder(String.Empty);

    foreach (char character in text)
    {
        if (Char.IsDigit(character))
        {
            builder.Append(character);
        }
    }

    (sender as TextBox).Text = builder.ToString();
}

Please note that you would have to add in code to set the caret position.

Answer 5

Correct answer is:

private void amount_PaidTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
    e.Handled = !сhar.IsNumber(e.KeyChar) && (e.KeyChar != '\b');
}