How do I determine if a request is the result of a postback?

Question

Update

I'm implementing a custom page caching solution and I don't want the request to be cached or retrieved from the cache if it's in response to a form submission or some sort of asp.net postback.

I'm trying to figure out if the current HttpRequest is a postback. Is there a way of doing this outside the context of a page or other usercontrol? In otherwords if I'm inside an HttpModule I don't have access to this.IsPostBack but I still need to determine if it is in fact a postback.

Also, are postbacks always "Post" requests or is that determined by containing form?

thanks!

Could you please elaborate on the "outside the context of a page or other usercontrol" ? — Vaibhav, Aug 05 '10 at 17:17
You cannot have a postback without an ASP.NET page. Otherwise, all you have is a regular HTTP POST. — Jason Berkan, Aug 05 '10 at 17:19
What does `IsPostBack` mean to you exactly? Like, only when data is passed to the module... or what? — Josh Stodola, Aug 05 '10 at 17:24

Ben McCormack · Answer 1 · 2010-08-05T17:43:36.253

10

Check the Method property of the HttpWebRequest. Postbacks should be marked as POST in the Method.

Also, the way you did it in old-school asp was to check for expected post-back parameters in the body of the HTTP message (Request.Form). You could check the content of the request for data that looks like postback parameter. I'm not sure what object exactly you're working with, but if it's an HttpWebRequest, you might check the request stream from the GetResponseStream() method of the object.

edited Aug 05 '10 at 17:43

answered Aug 05 '10 at 17:23

Ben McCormack

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For the lesser initiated: `if (context.Request.HttpMethod != "POST")` – Will Strohl Apr 12 '21 at 17:09

score 6 · Answer 2 · answered Aug 05 '10 at 17:24

6

if (Request.ServerVariables["REQUEST_METHOD"] == "POST") {
    // This is a POST
}

answered Aug 05 '10 at 17:24

jessegavin

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Ben McCormack has a better answer, but basically the same thing. – jessegavin Aug 05 '10 at 17:26

score 5 · Answer 3 · answered Aug 05 '10 at 18:16

The following static routine should be able to determine whether or not the current request is a postback. However, it will only work if you are executing an ASPX page, or derivitive thereof.

public class PostBackUtility
{
    public static Boolean IsPagePostBack
    {
        get 
        {
            Page pageHandler = HttpContext.Current.CurrentHandler as Page;
            if (pageHandler == null) return false;
            return pageHandler.IsPostBack;
        }
    }
}

Should also note that CurrentHandler may not yet be initialised depending upon which stage in the request lifecycle you attempt to evaluate IsPagePostBack. I believe this method will only be valid between HttpApplication.PostMapRequestHandler and HttpApplication.ReleaseRequestState.

score 4 · Answer 4 · answered Aug 05 '10 at 17:32

4

An HTTPHandler will have access to the current HTTPContext. You use that to check a few properties (Request.RequestType, Request.URLReferrer) and manually decide if it's a PostBack.

answered Aug 05 '10 at 17:32

ThatSteveGuy

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score 1 · Answer 5 · edited May 23 '17 at 10:27

1

You can get a reference to the current page: Get current System.Web.UI.Page from HttpContext?

Then you can check for the Page.IsPostBack property.

edited May 23 '17 at 10:27

Community

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answered Aug 05 '10 at 17:27

David

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This is good find and I'm up-voting it but it still wont work for me because I'm tapping into the pipeline before the handler gets associated with the request and therefore HttpContext.Current.Handler is always null. – Micah Aug 05 '10 at 17:30
During which step of page rendering do you need to know whether the page is postback or not? – David Aug 05 '10 at 17:39

Varun Nair · Answer 6 · 2020-08-25T11:42:33.267

Like @ThatSteveGuy's answer HTTPHandler will have access to the current page and you can check for the request type.

Note HTTPHandler context will be avaliable only in Application_PreRequestHandlerExecute in Global.asax.cs. Below is the code sample you can use it in your Global.asax.cs.

    void Application_PreRequestHandlerExecute(object sender, EventArgs e)
    {
        if (HttpContext.Current.Request.RequestType.Equals("POST"))
        {
            //Your code can go here.
        }
    }

How do I determine if a request is the result of a postback?

6 Answers6