C＃Ajax URL返回值，但函数未成功执行

Question

The following AJAX code:

 $.ajax({
            type: "POST",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            data: "{ 'userId' : '" + $('#userId').val() + "' }",
            url: "/User/UserURL",
            success: function (data) {                    
               Do something with data*
            },
            error: function () {
                alert('error');
            }
        });

Is hitting the /User/UserURL function correctly, which is:

 public JsonResult UserURL(int userId)
    {
        List<USER> u = (*Get from database using LINQ*).ToList();
        return Json(u, JsonRequestBehavior.AllowGet);
    }

When I put a debug point and check, the List<USER> u has the required value at the end while returning from the UserURL . However, at coming back to the page from where AJAX is being called, I get the 'error' alert. Why is it not hitting the success?

Edit: If it makes any difference, this is what's going on inside my success:

 for (i = 0; i < data.length; i++) {
      $('input[name="checkbox"]').each(function () {
          if (this.value == data[i].USER_ID) {
             (this).checked = true;
          }
      });
  }

Answer 1

It is difficult to help you find a solution to your problem, since the question didn't describe any specific type of error message.

So with what I am about to show you, you might not need any of our help to diagnose the issue.

Since you say at coming back to the page from where AJAX is being called, I get the 'error' alert , you need to do some more digging into why it is doing that, so this should help.

error: function (jqhxr) {
            alert(jqhxr);
        }

error Type: Function( jqXHR jqXHR, String textStatus, String errorThrown )

The jqXHR (in jQuery 1.4.x, XMLHttpRequest) object, a string describing the type of error that occurred and an optional exception object.

Once that is alerted it will help you diagnose what the real problem is.

Hope this helps!