Does anyone know if http error  401 unauthorized is returned in Chapper API only if OAuth token if NOT set? Or is it also if sessionId not valid?

The reason I ask is I was getting Invaild session id error if  access_token was but when using C# to upload a file with Authorization header set to "OAuth " + token., I am getting this Http 401.  I just want to make sure is only for http level error of missing header and not invalid session id..  

Is it possible to use APIChatter API to upload a new version of an existing file.  I see how to upload a new file but not a new version (e.g. go from V 1 to 2).    

Any help would be appreciated. 

Does anyone know if http error  401 unauthorized is returned in Chapper API only if OAuth token if NOT set? Or is it also if sessionId not valid?

The reason I ask is I was getting Invaild session id error if  access_token was but when using C# to upload a file with Authorization header set to "OAuth " + token., I am getting this Http 401.  I just want to make sure is only for http level error of missing header and not invalid session id..  

Is it possible to use APIChatter API to upload a new version of an existing file.  I see how to upload a new file but not a new version (e.g. go from V 1 to 2).    

Any help would be appreciated.