The path of the item '/Reports/Salesreport' is not valid. The full path must be less than 260 characters long; other restrictions apply. If the report server is in native mode, the path must start with slash. (rsInvalidItemPath)

One of SSRS report was crashing with the message "must be less than 260 characters". This message is bit confusing as we were having many urls which are bigger than 260 character limit and yet all those reports are rendered successfully.

Even the same report was successful with one set of parameter yet failed with another set of parameter. So, we arrived at conclusion that issue is with parameter value not URL length.

Reason : One or more parameters passed through query string may have restricted characters, which causes this particular issue.

Solution: Encode the parameter values before passing it to report. We used HttpUtility.UrlEncode(parameter.ToString()) while setting the value.

Hope it Helps