Archive for December 9, 2012

How to avoid ‘WebForms.PageRequestManagerServerErrorException’ error

December 9, 2012 Leave a comment

This error i got suddenly, when i use partial post back to server on aspx page. this page was working perfectly for months and today only i got this.  After looking into this sometime, only thing has changed here is now i have more data on the page.  But there is no way to catch the error and visual studio is returning this error when i click any control on the page.


When i look on the windows event log, exception was logged there as,

Operation is not valid due to the current state of the object.
at System.Web.HttpValueCollection.ThrowIfMaxHttpCollectionKeysExceeded()
at System.Web.HttpValueCollection.FillFromEncodedBytes(Byte[] bytes, Encoding encoding)
at System.Web.HttpRequest.FillInFormCollection()

What has happen was because of more data on the page, It is generating  “ThrowIfMaxHttpCollectionKeysExceeded” error.

To overcome this issue you have to add following key to web.config as follows,

   <add key=”aspnet:MaxHttpCollectionKeys” value=”2000″></add>

P/S : After looking into this issue on the web, i found this information,

 Microsoft released a security update KB2656356 / MS11-100 for ASP.NET to address a potential Denial of Service vulnerability.  In the update, Microsoft introduced a limit to the number of data elements on an ASP.NET form.   The default limit is 1000 data elements.   Exceeding the limit will cause a ThrowIfMaxHttpCollectionKeysExceeded error.

After applying the patch to your webserver, forms that exceed the limit will generate the following error when posting:

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