//the jsonDataObj looks like: 1,t
function sendData(jsonDataObj) {
var status = "";

jQuery.ajax({
 type: "POST",
 url: '/a/handlers/dowork.ashx/doit',
 data: jsonDataObj,
 contentType: "application/json; charset=utf-8",
 dataType: "json",
 success: function (output, status, xhr) {
  status = xhr.responseText;
  statusCode = xhr.status;
  console.log(status + "  " + statusCode);
 },
 error: function (xhr, textStatus, errorThrown) {
  status = "{'d':'0," + errorThrown + "'}";
  status = status.replace(/'/g, '"');
  statusCode = xhr.status;
  console.log(status + "  " + statusCode);
 }
});
}

using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Data;
 using System.Diagnostics;
 using System.Linq;
 using System.Web;
 using System.Web.Services;
 using System.Web.Script.Serialization;
 using System.Text;
 using System.Configuration;
 using System.Web.UI;
 using System.Web.UI.WebControls;
 using System.Xml;
 using Elmah;

namespace myapp
{
public class dowork : System.Web.UI.Page, IHttpHandler
{

public void ProcessRequest(HttpContext context)
{
}
public bool IsReusable
{
 get { return false; }
}

[System.Web.Services.WebMethod()]
public static string doit(object data)
{
 string status = string.Empty;
 string number = string.Empty;
 string letter = string.Empty;
 dynamic strings = ((IEnumerable)data).Cast<object>().Select(x => x == null ? x : x.ToString()).ToArray();

 number = strings(0).ToString();
 letter = strings(1).ToString();

 status = number + letter;
 return status;
}
}
}

Server Error in '/' Application.
 Parser Error
 Description: An error occurred during the parsing of a resource required to    service this request. Please review the following specific parse error details and modify your source file appropriately.
Parser Error Message: Could not create type 'myapp.a.handlers.dowork'.
Source Error:
Line 1: <%@ WebHandler Language="C#" CodeBehind="dowork.ashx.cs" Class="myapp.a.handlers.dowork" %>
Source File: /a/handlers/dowork.ashx Line: 1
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET  Version:4.6.1038.0

Line 1: <%@ WebHandler Language="C#" CodeBehind="dowork.ashx.cs" Class="myapp.a.handlers.dowork" %>