Use Javascript (jQuery) to display result of request in ASP.NET MVC

If it is an ajax call, It is best if you return a JSON response . You can use the Request.IsAjaxRequest() to determine whether the request is normal form request or ajax call.

You should also consider using to the PRG pattern. After successfully saving, you should do a redirect to a GET action where you can render a view, instead of returning to the same view with a viewbag message. If you want to pass some message to the new view/action, use TempData instead of ViewData.

[HttpPost]
public ActionResult Receiver(string name, string Email)
{       
    // Your existing code to save
    if(Request.IsAjaxRequest())
    {
        return Json(new { status = "success", message = "Created successfully" });
    }
    // Normal form submit. So let's follow PRG pattern
    TempData["ResultMessage"] = "Created successfully";
    return RedirectToAction("Index");
}

You can also put a try/catch and return a json like this for error usecase

return Json(new { status = "error", message = "some serious error" });

In Index action/view, you can read TempData["ResultMessage"] and display to user.

Now, for the ajax usecase, in your current view, you can add a div to show the message

<form id="contactForm" method="post" asp-action="Receiver">

    <div id="msg"></div>

    <div class="field half first">
        <label for="Name">Name</label>
        <input type="text" name="Name" id="Name" placeholder="Your name" required />
    </div>
    <div class="field half">
        <label for="Email">Email</label>
        <input type="email" name="Email" id="Email"  required />
    </div>
    <div class="field">
        <label for="Message">Message</label>
        <textarea name="Message" id="Message" rows="5" 
                  placeholder="Your message" required minlength="20"></textarea>
    </div>

    <input type="submit" value="Send Message" />

</form>

and now in your ajax call's success callback, check the json response coming back from server and show the message property as needed. If you are putting the script inside the razor view file, make sure you are putting it inside a Scripts section so that it will be evaluated in the proper order (After jQuery is loaded, assuming you load jQuery before calling RenderSection("scripts") inside the layout)

@section Scripts
{
    <script>
        $(function (){

            $("#contactForm").submit(function (e){

                e.preventDefault()
                $.ajax({
                    type: "POST",
                    url:  $(this).attr("action"),
                    data: car,
                    success: function (data){

                        if (data.status === "success")
                        {
                            $('#msg').html(message);
                        }  
                        //to do : handle statuss=="error" as needed                                                 
                    },
                    error: function (data)
                    {
                        alert("Failed.");
                    }
                });
            });
        });

    </script>
}

For asp.net core, you can write a IsAjaxRequest method in your base controller and use that. jQuery will add X-Requested-With header with value XMLHttpRequest for your ajax calls.

protected bool IsAjaxRequest()
{
    return Request.Headers["X-Requested-With"] == "XMLHttpRequest";
}