C sharp - Ayuda con Textbox en Windows Forms

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)

{

    if(char.IsDigit(e.KeyChar))

    {

        if ((e.KeyChar == '0' || e.KeyChar == '1') && textBox1.Text.Length <1 )

            e.Handled = false;

        else

            e.Handled = true;

    }

    else if (char.IsControl(e.KeyChar))

        e.Handled = false;

    else if (char.IsSeparator(e.KeyChar))

        e.Handled = true;

    else

        e.Handled = true;

}