handle json response in jquery ajax

Question

I want to retrieve data from database as a single row of string separated with '|' for which i am using json/ajax/WebMethod

JS

var request = {
    RefNo: $('#txtRefNo').val()
};
var strRequest = JSON.stringify(request);
$('#divDialog').html('<div>Retrieving Information...</div>').dialog({ title: 'Please Wait...', modal: true, resizable: false, draggable: false });
$.ajax({
    url: 'ajaxExecute.aspx/GETCUST',
    data: strRequest,
    dataType: "text",
    contentType: "application/json",
    cache: false,
    context: document.body,
    type: 'POST',
    error: function (xhr) {
        alert(xhr.responseText);
    },
    success: function (response) {                                        
            alert(response);
    }
});

C#

[WebMethod]
public static void GETCUST(string RefNo)
{
    try
    {
        DataTable dtOutput = new DataTable();
        dtOutput = Generix.getData("dbo.customers", "[first_name],[middle_name]", "reference_no='" + RefNo + "'", "", "", 1);
        if (dtOutput.Rows.Count > 0)
        {
            HttpContext.Current.Response.Write(dtOutput.Rows[0][0].ToString() + "|" + dtOutput.Rows[0][1].ToString());
        }
    }
    catch (Exception xObj)
    {
        HttpContext.Current.Response.Write("ERROR: " + xObj.Message);
    }
}

I am getting output with {"d":null} in it. How to remove it from response ? or am i doing something wrong in code

Output:

JAMES|BOND{"d":null}

Answer 1

You are getting {"d":null} because your WebMethod has no return value, you are just writing to the Response object.

You should return a string from your method :

[WebMethod]
public static string GETCUST(string RefNo) {
    try {
        DataTable dtOutput = new DataTable();
        dtOutput = Generix.getData("dbo.customers", "[first_name],[middle_name]", "reference_no='" + RefNo + "'", "", "", 1);
        if (dtOutput.Rows.Count > 0) {
            return dtOutput.Rows[0][0].ToString() + "|" + dtOutput.Rows[0][1].ToString();
        }
    } catch (Exception xObj) {
        return "ERROR: " + xObj.Message;
    }
}

And then the returned object will be {"d":"JAMES|BOND"}, which can be accessed via response.d in your javascript.

$.ajax({
    url: 'ajaxExecute.aspx/GETCUST',
    data: strRequest,
    dataType: 'JSON', // Changed dataType to be JSON so the response is automatically parsed.
    contentType: "application/json",
    cache: false,
    context: document.body,
    type: 'POST',
    error: function (xhr) {
        alert(xhr.responseText);
    },
    success: function (response) {
        alert(response.d); // Should correctly alert JAMES|BOND
    }
});

Please note that in the Javascript I have changed the dataType of the Ajax response to be JSON so that the response is parsed.