SSRS error: Operation is not valid due to the current state of the object
If you’re using SSRS in SharePoint integrated mode, you may come across this error when using report parameters that have a high number of items in them. A recent security bulletin highlighted some issues and vulnerabilities in ASP.net, and a patch was released to cover some of the items. One of these was the maximum number of items you can have in a collection. If you exceed the limit, then you’ll likely get an error like:
The URL-encoded form data is not valid. —> System.InvalidOperationException: Operation is not valid due to the current state of the object.
at System.Web.HttpValueCollection.FillFromEncodedBytes(Byte bytes, Encoding encoding)
— End of inner exception stack trace —
The workaround to this is to add the following to your web.config for your IIS application:
where 5000 is a number big enough to cover the number of items in your collection. Be aware of the security implications this could have. There’s some really useful info around the issue, here.