จะดึงข้อมูลจาก database ขึ้นมาแล้วให้ select radio button ตามค่านั้นต้องทำยังไงครับ

string taxrequire;
        private void txttaxrequired1_CheckedChanged(object sender, EventArgs e)
        {
            taxrequire = "y";
        }

        private void txttaxrequired2_CheckedChanged(object sender, EventArgs e)
        {
            taxrequire = "n";
        }

IF DataTable[0].TaxRequired == "1"
radio1.checked = true;
else
radio2.checked = true;

SqlCommand myCommand = connection.myConnection.CreateCommand();
            myCommand.CommandText = "UPDATE customer SET " + " custcode = '" + this.txtcustcode.Text + "' , custgroupcode = '" + this.txtcustgroupcode.Text + "', startdate = '" + this.txtstartdate.Value + "' , taxid = '" + this.txttaxid.Text + "' , taxrequired = '" + taxrequire + "', custstatuscode = '" + this.txtcuststatuscode.Text + "', lastupdate = '" + DateTime.Now + "', updateby = '" + bow + "', lastupdate = '" + DateTime.Now + "', updateby = '" + bow + "' " + " WHERE custcode = '" + Strcustcode + "' ";            
            myCommand.CommandType = CommandType.Text;
            myCommand.ExecuteNonQuery();


            connection.myConnection.Close();