asp.net - Inserting Sub-Array into Azure's Document DB -

i trying insert sub class (document) of "video" organization document.

however, when try add record, "object reference not set instance of object."

i tried use add , insert, neither worked. looked @ dcoument explorer , can see videos returning "null."

i assuming problem document db doesn't know video list. (in model, have defined list though)

also, have tried created new objects organization , video. also, have class called category, has exact same code (except object category) , inserting fine.

below action using.

[httppost] [validateantiforgerytoken] public async task<actionresult> create([bind(include = "name,description,link")] video video) {     if (modelstate.isvalid)     {         usersession usersession = new usersession();          usersession = (usersession)session["user"];          organization organization = (organization)documentdbrepository<organization>.getitem(d => d.id == usersession.organizationid);          video.dateadded = datetime.now;         organization.videos.add(video);          await documentdbrepository<organization>.updateitemasync(organization.id, organization);          return redirecttoaction("index");      }      return view(video); } 

set organization.videos non-null value. document db preserves stored. apparently, stored null.