'Operation is not valid due to the current state of the object' error during postback

I had a 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() Solution: <appSettings> <add key="aspnet:MaxHttpCollectionKeys" value="10000" /> </appSettings>

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