asp.net - 'Operation is not valid due to the current state of the object' error during postback

Question

I had an aspx page which was working well, but suddenly I am getting the error "Operation is not valid due to the current state of the object." whenever a postback is done.

The stack trace is:

at System.Web.HttpValueCollection.ThrowIfMaxHttpCollectionKeysExceeded()
at System.Web.HttpValueCollection.FillFromEncodedBytes(Byte[] bytes, Encoding encoding)
at System.Web.HttpRequest.FillInFormCollection()

Can someone help?

Answer 1

Somebody posted quite a few form fields to your page. The new default max introduced by the recent security update is 1000.

Try adding the following setting in your web.config's <appsettings> block. in this block you are maximizing the MaxHttpCollection values this will override the defaults set by .net Framework. you can change the value accordingly as per your form needs

<appSettings>
    <add key="aspnet:MaxHttpCollectionKeys" value="2001" />
 </appSettings>

For more information please read this post. For more insight into the security patch by microsoft you can read this Knowledge base article