Allow only numeric input in a windows form control

gistfile1.cs

public static void AllowOnlyNumericInput (object sender, System.Windows.Forms.KeyPressEventArgs e)
{
    if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) && e.KeyChar != '.')
    {
        e.Handled = true;
    }

    //only allow one decimal point
    if (e.KeyChar == '.' && (sender as System.Windows.Forms.TextBox).Text.IndexOf('.') > -1)
    {
        e.Handled = true;
    }

    //only allow one negative sign
    if (e.KeyChar == '-')
    {
        e.Handled = true;
        if (!(sender as System.Windows.Forms.TextBox).Text.Equals(String.Empty))
            (sender as System.Windows.Forms.TextBox).Text = (-1 * double.Parse((sender as System.Windows.Forms.TextBox).Text)).ToString();
    }
}