How to call webmethod in Asp.net C#

There are quite a few elements of the $.Ajax() that can cause issues if they are not defined correctly. I would suggest rewritting your javascript in its most basic form, you will most likely find that it works fine.

Script example:

$.ajax({    type: "POST",    url: '/Default.aspx/TestMethod',    data: '{message: "HAI" }',    contentType: "application/json; charset=utf-8",    success: function (data) {        console.log(data);    },    failure: function (response) {        alert(response.d);    }});

WebMethod example:

[WebMethod]public static string TestMethod(string message){     return "The message" + message;}

This is a bit late, but I just stumbled on this problem, trying to resolve my own problem of this kind. I then realized that I had this line in the ajax post wrong:

data: "{'quantity' : " + total_qty + ",'itemId':" + itemId + "}",

It should be:

data: "{quantity : '" + total_qty + "',itemId: '" + itemId + "'}",

As well as the WebMethod to:

public static string AddTo_Cart(string quantity, string itemId)

And this resolved my problem.

Hope it may be of help to someone else as well.

Necro'ing this Question ;)

You need to change the data being sent as Stringified JSON, that way you can modularize the Ajax call into a single supportable function.

First Step: Extract data construction

/*** * This helper is used to call WebMethods from the page WebMethods.aspx *  * @method - String value; the name of the Web Method to execute * @data - JSON Object; the JSON structure data to pass, it will be Stringified *      before sending * @beforeSend - Function(xhr, sett) * @success - Function(data, status, xhr) * @error - Function(xhr, status, err) */function AddToCartAjax(method, data, beforeSend, success, error) {    $.ajax({        url: 'AddToCart.aspx/', + method,        data: JSON.stringify(data),        type: "POST",        dataType: "json",        contentType: "application/json; charset=utf-8",        beforeSend: beforeSend,        success: success,        error: error    })}

Second Step: Generalize WebMethod

[WebMethod]public static string AddTo_Cart ( object items ) {    var js = new JavaScriptSerializer();    var json = js.ConvertToType<Dictionary<string , int>>( items );    SpiritsShared.ShoppingCart.AddItem(json["itemId"], json["quantity"]);          return "Add";}

Third Step: Call it where you need it

This can be called just about anywhere, JS-file, HTML-file, or Server-side construction.

var items = { "quantity": total_qty, "itemId": itemId };AddToCartAjax("AddTo_Cart", items,    function (xhr, sett) {  // @beforeSend        alert("Start!!!");    }, function (data, status, xhr) {   // @success        alert("a");    }, function(xhr, status, err){  // @error        alert("Sorry!!!");    });