AJAX调用返回“未定义”

Question

I'm trying to send value of Date to code behind while using an ajax call but it is returning. what am I doing wrong here

 function FetchTime() {
               debugger;
               var Pt_AppDate = document.getElementById("appdate").value;
               var reqs ='{AppointmentDate: "' + Pt_AppDate + '"}';
               $.ajax({
                    type: "POST",
                    url: "AppointmentForm.aspx/FetchATime",
                  data: reqs,
                    async: false,
                    contentType: "application/json; charset=utf-8",
                    datatype: "json",
                    success: OnSuccessApptwo,
                    failure: function (response) { alert(response.d); },
                    error: function (response) { alert(response.d); }
               });

          }

Code Behind

public void FetchATime()
          {
               conn.ConnectionString = dbObj.connString;
               conn.Open();
               string query2 = "Select Appointment_time from Appointments where convert(date, Appointment_date) < '" + AppointmentDate + "'";
               SqlCommand cmd2 = new SqlCommand(query2, conn);
               AvailableTime.DataSource = cmd2.ExecuteReader();
               AvailableTime.DataTextField = "Appointment_time";
                DoctorName.DataValueField = "Symptom_id";
               AvailableTime.DataBind();
               AvailableTime.Items.Insert(0, new ListItem("--Select Available Time", "0"));
               conn.Close();
          }

</div>

Answer 1

Your client-side code is trying to print a returned value:

alert(response.d)

but the server-side codes doesn't return a value:

public void FetchATime()
{
    //...
}

In order for something to be returned, you have to return something. (Something serializable of course.) For example:

public SomeType FetchATime()
{
    //...
    return someObject; // an instance of SomeType
}

Then in your client-side code you can access properties on that object:

alert(response.someProperty)