private void btnCalc_Click(object sender, EventArgs e) { bool flag; int year; int leap; clsDates myDate = new clsDates(); flag = int.TryParse(txtInput.Text, out year); if (flag == false) { MessageBox.Show("Digit characters only in YYYY format", "Input Error"); txtInput.Focus(); return; } leap = myDate.getLeapYear(year); txtLeapYearResult.Text = year.ToString() + " is " + ((leap == 1)? "" : "not ") + "a leap year"; txtEasterResult.Text = myDate.getEaster(year); }