System.Web.HttpException (0x80004005): 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)
The error is thrown immediately after clicking the submit button, and although I have logging implementation in the code, nothing was being reported on the app logs.
After researching on-line around forums, dev sites and official documentation I found out that in ASP.NET there is a security default setting that restricts form key/value fields to a maximum of 1000. Although it is probably more than enough for most cases, in this particular scenario I needed to be able to manage many more keys. Luckily the fix didn't require much effort. It is enough to add a new configuration settings on the "
That will increase the default ASP.NET Security Form Key collection to 2000 instead of the default 1000 value. After updating the configuration file I was able to solve the issue right away.
Keep this in mind or on a handy place, since dealing with those kind of errors are tricky and difficult to solve because the lack of error information.
Hope it helps !