Passing array of strings to webmethod with variable number of arguments using jQuery AJAX

Revised server-side code:

[WebMethod]public string Concat(List<string> arr){    string result = "";    for (int i = 0; i < arr.Count; i++)    {        result += arr[i];    }    return result;}

Also, add this above your WebService class declaration:

[System.Web.Script.Services.ScriptService]

Revised client-side code:

    $(document).ready(function () {        var myCars = new Array();        myCars[0] = "Saab";        myCars[1] = "Volvo";        myCars[2] = "BMW";        $.ajax({            type: "POST",            url: "WebService.asmx/Concat",            data: JSON.stringify({ arr: myCars }),            contentType: "application/json; charset=utf-8",            dataType: "json",            success: onSuccess,            failure: onError        });    });    function onSuccess(response) {        alert(response.d);    }    function onError() {        alert("fail");    }

Also, add above that script block a reference to JSON2, such as:

<script src="http://ajax.cdnjs.com/ajax/libs/json2/20110223/json2.js"></script>

Notes:

• I have tested this under .NET 4 and using jQuery 1.6.4.
• Make sure you keep the client and server variable names in sync:
  public string Concat(List<string> arr)
data: JSON.stringify({ arr: myCars })