sending JSON object successfully to asp.net WebMethod, using jQuery

I've been working on this for 3 hours and have given up. i am simply trying to send data to an asp.net web method, using jQuery. The data is basically a bunch of key/value pairs. so i've tried to create an array and adding the pairs to that array.

My WebMethod(aspx.cs) looks like this (this may be wrong for what i'm building in javascript, i just dont know):

   [WebMethod]
    public static string SaveRecord(List<object> items)
    .....

Here is my sample javascript:

var items = new Array;

    var data1 = { compId: "1", formId: "531" };
    var data2 = { compId: "2", formId: "77" };
    var data3 = { compId: "3", formId: "99" };
    var data4 = { status: "2", statusId: "8" };
    var data5 = { name: "Value", value: "myValue" };

    items[0] = data1;
    items[1] = data2;
    items[2] = data3;
    items[3] = data4;
    items[4] = data5;
Here is my jQuery ajax call:

var options = {
        error: function(msg) {
            alert(msg.d);
        },
        type: "POST",
        url: "PackageList.aspx/SaveRecord",
        data: { 'items': items },
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        async: false,
        success: function(response) {
            var results = response.d;
        }
    };
    jQuery.ajax(options);

i get the error -Invalid JSON primitive: items.-

so...if i do this:

var DTO = { 'items': items };

and set the data parameter like this:

data: JSON.stringify(DTO)

then i get this error:

Cannot convert object of type \u0027System.String\u0027 to type \u0027System.Collections.Generic.List`1[System.Object]\u0027

Answers:

Answer

When using AJAX.NET I always make the input parameter just a plain old object and then use the javascript deserializer to covert it to whatever type I want. At least that way you can debug and see what type of object the web method in is recieving.

You need to convert your object to a string when using jQuery

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:ScriptManager ID="sm" runat="server" EnablePageMethods="true">
            <Scripts>
                <asp:ScriptReference Path="~/js/jquery.js" />
            </Scripts>
        </asp:ScriptManager>
        <div></div>
    </form>
</body>
</html>
<script type="text/javascript" language="javascript">
    var items = [{ compId: "1", formId: "531" },
        { compId: "2", formId: "77" },
        { compId: "3", formId: "99" },
        { status: "2", statusId: "8" },
        { name: "Value", value: "myValue"}];

        //Using Ajax.Net Method
        PageMethods.SubmitItems(items,
            function(response) { var results = response.d; },
            function(msg) { alert(msg.d) },
            null);

        //using jQuery ajax Method
        var options = { error: function(msg) { alert(msg.d); },
                        type: "POST", url: "WebForm1.aspx/SubmitItems",
                        data: {"items":items.toString()}, // array to string fixes it *
                        contentType: "application/json; charset=utf-8",
                        dataType: "json",
                        async: false, 
                        success: function(response) { var results = response.d; } }; 
        jQuery.ajax(options);
</script>

And the Code Behind

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Script.Serialization;
using System.Web.Script.Services;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace CustomEquip
{
    [ScriptService]
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }
        [WebMethod]
        public static void SubmitItems(object items)
        {
            //break point here
            List<object> lstItems = new JavaScriptSerializer().ConvertToType<List<object>>(items);
        }
    }
}
Answer

In your example, it should work if your data parameter is:

data: "{'items':" + JSON.stringify(items) + "}"

Keep in mind that you need to send a JSON string to ASP.NET AJAX. If you specify an actual JSON object as jQuery's data parameter, it will serialize it as &k=v?k=v pairs instead.

It looks like you've read it already, but take another look at my example of using a JavaScript DTO with jQuery, JSON.stringify, and ASP.NET AJAX. It covers everything you need to make this work.

Note: You should never use JavaScriptSerializer to manually deserialize JSON in a "ScriptService" (as suggested by someone else). It automatically does this for you, based on the specified types of the parameters to your method. If you find yourself doing that, you are doing it wrong.

Answer

The following is a code snippet from our project - I had trouble with not wrapping the object as a string and also with Date values - hopefully this helps someone:

        // our JSON data has to be a STRING - need to send a JSON string to ASP.NET AJAX. 
        // if we specify an actual JSON object as jQuery's data parameter, it will serialize it as ?k=v&k=v pairs instead
        // we must also wrap the object we are sending with the name of the parameter on the server side – in this case, "invoiceLine"
        var jsonString = "{\"invoiceLine\":" + JSON.stringify(selectedInvoiceLine) + "}";

        // reformat the Date values so they are deserialized properly by ASP.NET JSON Deserializer            
        jsonString = jsonString.replace(/\/Date\((-?[0-9]+)\)\//g, "\\/Date($1)\\/");

        $.ajax({
            type: "POST",
            url: "InvoiceDetails.aspx/SaveInvoiceLineItem",
            data: jsonString,
            contentType: "application/json; charset=utf-8",
            dataType: "json"
        });

The server method signature looks like this:

    [WebMethod]
    public static void SaveInvoiceLineItem(InvoiceLineBO invoiceLine)
    {
Answer

Decorate your [WebMethod] with another attribute:

[ScriptMethod(ResponseFormat = ResponseFormat.Json)]

I believe this is in System.Web.Services.Scripting...

Answer

This is the way you define your data (JSON)

data: { 'items': items },

and the this the way it should be

data: '{ items: " '+items +' "}',

basically you are serializing the parameter.

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