How to determine postback with javascript and asp.net mvc?

Question

I am currently using ASP.NET MVC2 and I have a ActionController that allows me to save only if the form content is valid, something like

public ActionResult Edit(Guid id)
{
    //....
    return View();
}

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(Guid id, DTOUserEdit dto)
{
    if ( ModelState.IsValid) Save(user);
    return ModelState.IsValid ? RedirectToAction("Index") : (ActionResult)View(dto);
}

This occasion that, if I'm completing incorrectly the editing form it shows again repeatedly.

My question is if I can trust in the following piece of javascript code to determine whether a call is a PostBack, in other words if it helps me to know it's not the first time that I'm visiting that page. I read somewhere that I should not trust in document.referrer because some proxies delete it, then what code should I use?

function isPostBack() {
    if (document.referrer != null && document.referrer == window.location.href)
        return true;
    return false;
}

i have no idea what your asking. there is no "postback" in MVC (thankfully). There is a GET (first time), or POST (submit). What are you trying to achieve? — RPM1984
– RPM1984, Commented Dec 21, 2010 at 8:42

Alexander Prokofyev · Accepted Answer · 2010-12-21 06:23:54Z

2

This code could be easily hacked by malicious user or Javascript could be disabled at all.

I don't know exactly your requirements, but I would probably prefer server side check during view rendering. So instead of

<script type="text/javascript">
    if (isPostBack())
    {
        alert("Check your data!");
    }
</script>

I would use

<% 
    if (Request.HttpMethod == "POST") 
    {
%>
    <script type="text/javascript">
        alert("Check your data!");
    </script>
<% 
    }
%>

answered Dec 21, 2010 at 6:23

Alexander Prokofyev

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1 Comment

tecnocrata Over a year ago

Thank you very much for responding, but unfortunately I need a client-side check because I have to include this function (IsPostBack) within a file. js, currently I do not know how to use the server code, as you propose, into a file. js, that could solve my problem. Thanks again.

Murtaza Mandvi · Accepted Answer · 2011-06-09 20:03:58Z

0

You could expose a public property on your page :

public bool IsPostBack { get; set; }

Set this property to true / false by checking the !IsPostBack in your Codebehind and assign the value to a hidden variable on the page.

On the client side read the value fromt he hidden variable.

Hope this helps

answered Jun 9, 2011 at 20:03

Murtaza Mandvi

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