When we write our own custom HTTPHandlers aren't they behave the same way as ICallBackEventHanlder does? we use both to make ajax calls from our web page, isn't this correct? or my understanding wrong, I wont doubt if it is :(
Obviously HTTPHandlers are more broader concept since a web page (.aspx) etc are also http handlers.
A ICallBackEventHandler is for integration with a page -- a handler is for anything. A callback handler is useful when you want to do an ajax request from the client-side of a page, and from that handler you still want access to all of the controls on the page, their re-saturated state that comes from ViewState, etc. An http handler has no access to the page or its state. A callback handler can also push some state changes back to the client. For example, a callback handler might render something which requires the __EVENTVALIDATION field on the client-side to be updated.
Related
I am new to asp .net web forms and I am having trouble in efficiently handling the broswer refersh. I have used the below link to do the same.
http://geekswithblogs.net/Vipin/archive/2011/06/08/detecting-browser-refresh-from-code-behind-in-.net.aspx
However , the problem with the above approach is that the button click is throwing the below error:
Invalid postback or callback argument. Event validation is enabled using in configuration or <%# Page EnableEventValidation="true" %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.
Any help would be appreciated.
I suggest you to use Post/Redirect/Get pattern
If a web user attempts to refresh the page this pattern avoid the HTTP POST request to be resubmitted.
Just force a redirect at the end of the page that receive the posted data.
Moreover rely on session like example does is never a good practice
I am looking into identifying handler that will handle my request.
I would like to know if request is asking for static resource (that is css,js or image files).
Upon inspecting HttpContext.Request on PreRequestHandlerExecute Event i see that handler and currentHandler variables are null for static resources and for any other custom handlers or aspx pages i have handler and currentHandler variables.
My question is: Is the is good place to differ handlers that will handle request or not?
I would like not to identify handler file extension by taking it from system.web/httpHandlers, cause i would like not to use system.web/httpHandlers just system.webServer/handlers. And i don't want to use Microsoft.Web.Administration namespace cause that will make me modify configurations on all servers.
Forgot to make an update on how i resolved it. I actually do deffer native from custom handlers on PostMapRequestHandler event. If your request will be handled by native handler than handler and currentHandler vars of HttpContext.Request will be null. Also by setting runAllManagedModulesForAllRequests to false request that will be handled by native handlers want even raise PostMapRequestHandler event. Hope this helps someone.
We have an HTTPModule whose sole purpose is to do "url rewriting". By definition of an HTTPModule, ALL browser requests (html, css, javascript, images, etc) go through the event handlers of this class.
During the signin process, we are catching the moment when the user switches from "anonymous" to "signed-in" user in the Global.asax's Profile_OnMigrateAnonymous event handler. One issue we're finding is that when the user signs in, the Profile_OnMigrateAnonymous event fires, seemingly, for possibly EVERY resource within the request to generate the page to the user - namely, the html, css, javascript, images, etc. It was my understanding that this event will fire only ONCE. Why would it be firing multiple times? Is it a result of our registered "url rewriting" HTTPModule? Is there a way we can configure the application to only fire that event once?
For normal resource reqeusts (css/js/img etc) IIS handles the request directly. It only passes to the asp_net worker requests for specfic filenames (such as .aspx and .asmx).
Your HTTPModule is basically forcing IIS to forward all requests to the worker process, hence each request is firing off the Profile_OnMigrateAnonymous.
I don't think you can bypass the call to Profile_OnMigrateAnonymous, however you could implement a bit of code to check for a an .aspx/.ascx etc file name and only then perform the actual actions specified.
I have for example ASP.NET site with textbox, button and many other controls.
When user click on button i want to retrieve some data(string,number) from DB(MSSQLServer) and show these data to user without postback(ajax).
How can i do this?
Thanks
There are two key components. A server-side method that can respond to a request for data and a client-side javascript function that can make an AJAX request to that method and consume the data, updating the web page.
On the server side you can use an actual web service or web application methods marked with the WebMethod attribute. These accept a request and respond, not with a web page, but usually a partial HTML snippet, XML, or JSON.
On the client side, I would look at using a framework that implements AJAX -- such as MicrosoftAjax or jQuery, though there are many others. It would be then be a matter of correctly configuring the client function to respond to the interaction trigger (button click) so that it calls the proper method with the right parameters and processes the response.
Partial Page Updates vai AJAX
Using Web Services via AJAX
jQuery -- many examples and documentation
I've got an HTTPModule that does some role-based page access security (I'm having to retrofit some security into some code that we've acquired).
I've noticed that in one instance that it doesn't fire on a Server.Transfer.
Here's a snippet of the code:
' move to target page
Select Case eTransferMethod
Case TargetPageTransferMethod.Redirect
Page.Response.Redirect(strPage, False)
Case TargetPageTransferMethod.Transfer
Context.Handler = Me
Page.Server.Transfer(strPage)
Case TargetPageTransferMethod.None
' Do nothing
End Select
The case that I'm talking about here is the TargetPageTransferMethod.Transfer case. The page will be an .aspx page.
Now I know that AcquireRequestState is fired on other Server.Transfer calls in this code. In fact it gets fired on the postback when a button on the page transferred to is clicked. Ironically my security code is bypassed on the transfer to this page but denies access on the postback when this page's cancel button is clicked! :eek:
I'd post further details of the codebase but it's so convoluted and sprawling it'd be a nightmare to explain.
So basically I'm asking 'What might cause the AcquireRequestState event in an HTTPModule to not fire when a Server.Transfer is called?'
The way to get around this is to create a custom HttpHandler that inherits the System.Web.UI.PageHandlerFactory class.
You can then override the GetHandler method which is called whenever a page instance is created, both on Response.Redirect and on Server.Transfer.
Register this new handler to use the "*.aspx" extension and all pages will automatically use the new handler. This allows you to do custom authorisation on Server.Transfer as well as use a dependency injection framework (e.g. MS Unity).
I can understand it being called on a post back, as that is another request from the client, but Server.Transfer doesn't initiate a new request, it transfers execution from one page to another.
As the AcquireRequestState event is fired "when ASP.NET acquires the current state (for example, session state) that is associated with the current request" - this would occur on the initial request from the browser, but not on the server transfer as the server didn't get another request, you're just asking it to process a different page.
A key comment is this one from the HttpServerUtility.Transfer documentation:
ASP.NET does not verify that the current user is authorized to view the resource delivered by the Transfer method. Although the ASP.NET authorization and authentication logic runs before the original resource handler is called, ASP.NET directly calls the handler indicated by the Transfer method and does not rerun authentication and authorization logic for the new resource. If your application's security policy requires clients to have appropriate authorization to access the resource, the application should force reauthorization or provide a custom access-control mechanism.
Server.Transfer doesn't reprocess the entire HTTP pipeline for the destination page. It just calls the destination page's HttpHandler. Because of this, you shouldn't see any of the earlier applicaton events get fired.