使用JSOn字符串asp.net MVC4更新数据库

Question

嘿我试图将表单作为Json发布到我的控制器，然后更新列匹配的数据库。我似乎无法让它发挥作用。我正在使用如下所示的函数将表单数据转换为json字符串并且它正在发布但我遇到了控制器方法的问题，我需要找出如何将json中的valuse与数据库中的值进行匹配任何帮助都会很棒

$.ajax({
    type: 'POST',
    contentType: 'application/json',
    url: "Admin/update/",
    dataType: "json",
    data: formToJSON(),
    success: function (themessage) {

    }
});

使用JSON.stringify转换表单

function formToJSON() {
 return JSON.stringify({
    "username": $('#username').val(),
    "fname": $('#fname').val(),
    "lname": $('#lname').val(),
    "address1": $('#address1').val(),
    "address2": $('#address2').val(),
    "postcode": $('#postcode').val(),
    "town": $('#town').val(),
    "memcat": $('#memcat').val(),
    "phone": $('#phone').val(),
    "email": $('#email').val(),
    "message": $('#message').val(),
    "password": $('#password').val(),
    "Admin": $('#Admin').val(),
 });
}

发布包含

{"username":"Broon","fname":"Paw","lname":"Broon","address1":"12 Glebe Street","address2":"Sinderins","postcode":"DD12 4RT","town":"Dundee","memcat":"Ordinary","phone":"123456","email":"paw@localhost","password":"paw","Admin":"no"}

控制器方法     //         // POST：/ Admin /

    public JsonResult update(string username)
    {



        var themessage = from b in db.member
                         select b;


        themessage = themessage.Where(b => username.Contains(b.username));

        foreach (var item in themessage)
        {
            item.username = username;
        }


        db.SaveChanges();


        return Json(themessage, JsonRequestBehavior.AllowGet);
    }

问题是访问json数据以匹配数据库数据。我猜我可能需要以某种方式解析json？上面我只试图匹配用户名。