How to Accept '(“ and ”)" on Digits Only Accepted Textbox

Question

I have field where only digits are accepted but i want to same feature for another field (fax) where example values will look like (070) 412 34 56.

how can modify my current function so it also accepts "(" and ")" ?

here is current code i have to check digits

char ch = e.KeyChar;
if (!Char.IsDigit(ch) && ch != 8 && ch != 46)
{
    e.Handled = true;
}

e.Handled = !char.IsDigit(e.KeyChar) && !char.IsControl(e.KeyChar);

Answer 1

One possibility:

Place every allowed character in a string and see if the entered character exists.

e.Handled = "0123456789()".IndexOf(e.KeyChar) < 0;

string.IndexOf returns the index of the given char.
It returns -1 if the character was not found.