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

I’m trying to pass an array of string parameters to a C# ASP.NET web service using jQuery Ajax. Here is my sample web method. Note that the function accepts a variable number of parameters. I get a 500 Internal Server Error in Chrome’s javascript console when I run the jquery. I’m using jquery 1.6.2 and .NET3.5

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

Here is the jquery:
$(document).ready(function() {

    var myCars=new Array(); 
    myCars[0]="Saab";      
    myCars[1]="Volvo";
    myCars[2]="BMW";

    $.ajax({
        type: "POST",
        url: "WebService.asmx/Concat",
        data: {arr: myCars},        //can't figure out what to put here     
        success: onSuccess,
        Error: onError
    });
});

function onSuccess()
{
    alert("testing");
}

function onError() 
{
    alert("fail");
}

</script>

Any help is appreciated!

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

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="https://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 })


All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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