private void teacherSelect_SelectedIndexChanged(object sender, EventArgs e)
{
totalhrstxt.Text = "";
chrgtxt.Text = "";
KeyValuePair <int, string> selectEntry = (KeyValuePair <int, string>)teacherSelect.SelectedItem;
string tID = selectEntry.Key.ToString();
idtxt.Text = tID;
slr = new Salary();
slr.CalculateTotalHrs(tID);
totalhrstxt.Text = slr.TotalNoHrs.ToString();
}
