Making a window based application Trainee Management system

Question

When i run my program it doesn't show any error.
But when i work on it the first page works fine. But when i reach on second page it gives an error which is as follows.:

ds.RegstoredProcedure(F_Nametxtbx.Text, L_Nametxtbx.Text, Gendertxtbx.Text, Convert.ToDateTime(DOQtxtbx.Text), AddressrichTxtBx.Text, Email_IDtxtBx.Text, MobileNotxtBx.Text, Coursejoinedcmbx.Text, Convert.ToDateTime(DOJdateTimePicker.Text),Convert.ToInt32(durationlbl.Text), PasswordtxtBx.Text);

In this line the error occured which says that "Input string was not in a correct format".