string conStr = "Data Source=.;Initial Catalog=DershaneVT;Integrated Security=True";
      using (SqlConnection con = new SqlConnection(conStr))
            {
                try
                {
                    con.Open();
                    SqlCommand cmd = con.CreateCommand();
                    cmd.CommandText = "spInsertStudent";
                    cmd.CommandType = CommandType.StoredProcedure;
                    cmd.Parameters.AddWithValue("@name", sdntName.Text);
                    cmd.Parameters.AddWithValue("@surname", stdnSurname.Text);
                    cmd.Parameters.AddWithValue("@birthdate", Convert.ToDateTime(stdntBirthDate.Text));
                    cmd.Parameters.AddWithValue("@tel", stdntPhone.Text);
                    cmd.Parameters.AddWithValue("@classId", stdntClass.SelectedValue);
                    cmd.ExecuteNonQuery();

                    MessageBox.Show("Eklendi!");
                
                }
                catch (Exception ex)
                {

                }
                finally
                {
                    if (con.State != ConnectionState.Closed)
                    {
                        con.Close();
                    }
                }
            }