Why TextBox validation doesn't work

Question

I wish to validate this TextBox against negative values and characters (must be integer without decimal) It works well for . but I am not able to understand why it accepts negative value and characters?

My code is :

private void txtLifeMonths_KeyPress(object sender, KeyPressEventArgs e)
{
    if (!Char.IsDigit(e.KeyChar) && (e.KeyChar == '.') && (e.KeyChar >= 0) && (e.KeyChar != (char)Keys.Back))
        e.Handled = true;
}

Salah Akbari · Accepted Answer · 2016-05-09 06:23:59Z

1

You need to replace the first && operator with || and also move it to the end of your if statement then it should works as you want. Like this:

private void txtLifeMonths_KeyPress(object sender, KeyPressEventArgs e)
{
    if (!Char.IsDigit(e.KeyChar) && (e.KeyChar >= 0) && (e.KeyChar != (char)Keys.Back) || (e.KeyChar == '.'))
        e.Handled = true;
}

edited May 9, 2016 at 6:23

answered May 9, 2016 at 5:47

Salah Akbari

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2 Comments

test test Over a year ago

Yaah thanks it worked, But why i needed to replace && with or ?

Salah Akbari Over a year ago

@testtest ... Because you don't want to evaluate the second operand which validates for . with the first operand. If the second operand evaluates to true e.Handled should be true

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