In my specific case, I need the value in propertyPriceTextBox to be numeric only, and a whole number. A value also has to be entered, and I can just Messagebox.Show() a warning and that's all I'd need to do.

This is what I have so far.

        private void computeButton_Click(object sender, EventArgs e)
    {
        decimal propertyPrice;

        if ((decimal.TryParse(propertyPriceTextBox.Text, out propertyPrice)))
            decimal.Parse(propertyPriceTextBox.Text);
        {

            if (residentialRadioButton.Checked == true)



                commisionLabel.Text = (residentialCom * propertyPrice).ToString("c");



            if (commercialRadioButton.Checked == true)

                commisionLabel.Text = (commercialCom * propertyPrice).ToString("c");

            if (hillsRadioButton.Checked == true)

                countySalesTaxTextBox.Text = ( hilssTax * propertyPrice).ToString("c");

            if (pascoRadioButton.Checked == true)

                countySalesTaxTextBox.Text = (pascoTax * propertyPrice).ToString("c");

            if (polkRadioButton.Checked == true)

                countySalesTaxTextBox.Text = (polkTax * propertyPrice).ToString("c");

            decimal result;

                result = (countySalesTaxTextBox.Text + stateSalesTaxTextBox.Text + propertyPriceTextBox.Text + comissionTextBox.Text).ToString("c");
        }

        else (.)

            MessageBox.Show("Property Price must be a whole number.");
    }