Input Validate: How to accept only one or two digit integer?

Question

I'm programming a game. I want to accept only a one or two digit number.

 

Only digits 0-9 allowed.

Only 1 or 2 digits allowed.

 

When second digit entered, number is accepted. Program goes to range check (Message to user if number is odd or greater than 20)

For one digit number, user has to indicate done by pressing return.

 

Here is what I have:

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
char ch = e.KeyChar;
if (ch == 46 && textBox1.Text.IndexOf('.') != -1)
{
e.Handled = true;
return;
}
if (!char.IsDigit(ch) && ch != 8 && ch != 46)
// 8 = Backspace, 46 = decimal point
{
e.Handled = true; // Exits without taking any further action
}
}