Unable to cast object of type : Jquery Ajax method to call a webservice

Question

User1052662409 posted

Hi All,

I am calling a webservice through jquery ajax method. Below is my service method.

[WebMethod]
    public DataTable GetTrainingDates(int user_id)
    {
        DBHelper oDBHelper = new DBHelper();
        Hashtable param = new Hashtable();
        param.Add("@case",6);
        param.Add("@book_by ", user_id);
        DataTable dt = new DataTable();
        dt = oDBHelper.GetDatatabel("[dbo].[usp_training_update]", param);
        dt.TableName = "MyTable";
        return dt;
    }

and below is my jquery code to call this method. I am trying to get parameter from a Literal names ltuser. see the below 

<script type="text/javascript">
        debugger;
        var uid = $('#<%=ltuser.ClientID%>').html();
        var id = parseInt(uid);
        $.ajax({
            type: "POST",
            url: "ServiceGetTrainingDate.asmx/GetTrainingDates",
            data: "{'user_id': " + id + " }",
            contentType: "application/json",
            datatype: "json",
            success: function (data) {
                $('div[id*=calender]').fullCalendar({
                    header: {
                        left: 'prev,next today',
                        center: 'title',
                        right: 'month,agendaWeek,agendaDay'
                    },
                    editable: true,
                    events: data.d
                });
                $("div[id=loading]").hide();
                $("div[id=celender]").show();
            },
            error: function (XMLHttpRequest, textStatus, errorThrown) {
                debugger;
            }
        });

        debugger;
        $('div[id*=calender]').fullCalendar({
            header: {
                left: 'prev,next today',
                center: 'title',
                right: 'month,agendaWeek,agendaDay'
            },
            editable: true,
            events: $.map(data.d, function (item, i) {
                var event = new Object();
                event.bigid = item.EventID;
                event.vcexpirydate = new Date(item.EndDate);
                event.title = item.EventName;
                return event;
            })
        });
    </script>

I tried to convert this ltuser value to int as my method requires an int, but still it shows Unable to cast object of type.

Please help.

Answer 1

User-2054057000 posted

You are using a literal control which is bad because literal control is not rendered as any HTML control in the browser.

I did some testing for the literal control in my web form. I added the following code in my .aspx page:

<div id="LtDiv">
    <asp:Literal ID="ltuser" runat="server">12</asp:Literal>
</div>

In my browser it was rendered as:

<div id="LtDiv">
   12
</div>

You can see the literal (id='ltuser') is not rendered at all, only its value is shown.

I suggest you to use span instead of literal:

<span id="ltuser">12</span>

and you can get it's value like this:

$("#ltuser").text();

And then you can make the AJAX request to your web service.

Answer 2

User-474980206 posted

I have not used webforms and thus [WebMethod] in years, but following current json binding rules, you are pass an object not an int. there are 2 solutions:

1) change ajax data:

// convert to string for data 
data: id + '',

// use standard JSON utility
data: JSON.stringify(id),

2) change the web method to receive an object:

public class UserIdRq
{
    public int user_id {get; set;}
}
[WebMethod]
public DataTable GetTrainingDates(UserIdRq user_id)
{
....
}