load textboxes according selected value from dropdownlist

public ClsPatient getSpecificPatient(string patientIdNumber)
       {
           using (SqlConnection conn = new SqlConnection(ConnString))
           {
               SqlCommand cmd = new SqlCommand("procGetPatientByPatientID", conn);
               cmd.CommandType = CommandType.StoredProcedure;
               cmd.Parameters.Add(new SqlParameter("@patientIDNumber", SqlDbType.NVarChar));
               cmd.Parameters["@patientIDNumber"].Value = patientIdNumber;
               ClsPatient patient;
               try
               {
                   conn.Open();
                   SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.SingleRow);

                   reader.Read();
                   patient = new ClsPatient(Convert.ToString(reader["PatName"]),
                                                           Convert.ToString(reader["PatSurname"]), Convert.ToString(reader["PatAddress"]),
                                                           Convert.ToString(reader["PatTell"]), Convert.ToString(reader["PatCell"]),
                                                           Convert.ToString(reader["PatWorkTell"]), Convert.ToString(reader["PatEmail"]),
                                                           Convert.ToString(reader["PatGender"]));
                   reader.Close();
               }
               catch (SqlException)
               {
                   throw new ApplicationException("Error reading deleted record from system files. Press ok and refresh button.");
               }
               return patient;
           }
       }

protected void ddlPatientID_SelectedIndexChanged(object sender, EventArgs e)
   {
       //systemBusinessLayer=new BusinessLayer();
       ClsPatient patient = systemBusinessLayer.getSpecificPatient((string)ddlPatientID.SelectedValue);
       txtViewPatientName.Text = patient.PatName;
       txtViewPatientSurname.Text = patient.PatSurname;
       txtViewPatientPhonenumber.Text = patient.PatTell;
       txtViewPatientCellphone.Text = patient.PatCell;
       txtViewPatientWorkPhonenumber.Text = patient.PatWorkTell;
       txtViewPatientEmail.Text = patient.PatEmail;
       string gender = patient.PatGender;

       if (gender == "Female")
       {
           radFemale.Checked = true;
            radMale.Checked=false;

       }
       else if(gender=="Male")
       {
           radMale.Checked=true;
           radFemale.Checked = false;
       }

       txtViewPatientAddress.InnerText = patient.PatAddress;

   }