401 Unauthorized Error On SSRS URL Access ... but it works in Fiddler?

Question

I am attempting to generate a pdf from a SSRS report using URL Access in C#. (In the business layer behind a WebApi Controller) I create an instance of the HttpClient, assign correct credentials and form the request URL like:

http://sqlserver1/ReportServer/Pages/ReportViewer.aspx?/Clients/Acme/AcmeActivitySummary&rs:Command=Render&rs:format=pdf&Region=west&CutOffDate=10/25/2015

If I put my URL in a browser, it downloads the expected PDF file. When I execute this URL from the HttpClient instance to return a stream, I get a 401 Unauthorized Error.

If I open up Fiddler to see why...it works as expected.

How do I make this work without having to use Fiddler...and why doesn't it work now?

Answer 1

Somewhere along the lines Microsoft changed the "standard" for URL Access to SSRS. The URL Pattern " http://{Server}/ReportServer/Pages/ReportViewer.aspx?/{Path to Report File} & [commands] & [parameters]

was deprecated in favor of

http://{server}/reportserver?/{path} & [commands] & [parameters].

HOWEVER...the old url pattern will still work 'sometimes'. SSRS will still receive the request at the old 'endpoint' and, if the request can be forwarded it will do so. So a 'normal' request from a browser (or from Fiddler) appears to work just fine. The problem is with the HttpClient request, which SSRS will not forward to the new endpoint...and it just returns the [somewhat confusing] 401 Unauthorized exception...which apparently means "I am not authorized to forward this request" not "you are not authorized to access this resource".

(after losing more time than I care to admit finding this...I thought a post here would be helpful to others.)