Why Doesn\'t an Ajax Call in ASP.NET MVC Trigger an Alert if Data is Missing?

Making a Simple Ajax Call to Controller in ASP.NET MVC

When attempting to make Ajax calls in ASP.NET MVC, one may encounter challenges as exemplified in the scenario below:

Problem

The goal is to display an alert with data returned from a controller method. However, the alert is not firing.

Controller:

public class AjaxTestController : Controller
{
    public ActionResult FirstAjax()
    {
        return Json("chamara", JsonRequestBehavior.AllowGet);
    }   
}

View:

<code class="html"><script type="text/javascript">
    $(document).ready(function () {
        var serviceURL = '/AjaxTest/FirstAjax';

        $.ajax({
            type: "POST",
            url: serviceURL,
            data: param = "",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: successFunc,
            error: errorFunc
        });

        function successFunc(data, status) {     
            alert(data);
        }

        function errorFunc() {
            alert('error');
        }
    });
</script></code>

Observation:

Initially, the Ajax call failed to trigger the alert. After adding an unrelated parameter and making method changes in the controller, the alert began functioning correctly. However, the reason for this behavior remains unclear.

Solution

1. Remove Unnecessary Data Attribute:

Since no data is being sent to the server, the data attribute should be removed from the Ajax call.

2. Utilize Razor Syntax for URL:

In the Ajax method, use Razor syntax to generate the URL instead of a static string:

<code class="js">$.ajax({
    url: '@Url.Action("FirstAjax", "AjaxTest")',
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: successFunc,
    error: errorFunc
});</code>

3. Add Message Display in Success Function:

In the success function, add the message you want to display in the alert.

4. Handling Data POSTing:

If you need to POST data to the server, add a data attribute and provide the appropriate data in the Ajax call.

5. Updated Ajax Call:

<code class="js">$.ajax({
    type: "POST",
    url: '@Url.Action("FirstAjax", "AjaxTest")',
    contentType: "application/json; charset=utf-8",
    data: { a: "testing" },
    dataType: "json",
    success: function() { alert('Success'); },
    error: errorFunc
});</code>

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