c# - Cannot authenticate in Web API service called from MVC website -

i have asp.net mvc website using angular front end, needs communicate rest web api service retrieve data. have authentication logic against custom provider in mvc project , works fine using adlds. calls rest web api have no authentication data passed , can't work out how pass user authenticated mvc, on rest web api.

here example call web api.

 public void approvemodel(int modelversionid, string comments)         {             var request = new restrequest("api/modelversion", method.post) { requestformat = dataformat.json };             request.addbody(new[] { new modelaction { modelactiontype = modelactionconstants.modelactionapprovemodel, actionparameters = new dictionary<string, string> { { modelactionconstants.modelactionparametermodelversionid, modelversionid.tostring(cultureinfo.invariantculture) }, {modelactionconstants.modelactionparametercomments, comments} } } });             request.usedefaultcredentials = true;              var response = _client.execute(request);             if (response.statuscode != httpstatuscode.ok)                 throw new serverexception(response.content);                     } 

my web api controller method (abbreviated)

 [validateaccess(constants.dummy, constants.secure_environment)]                 public httpresponsemessage post(modelaction[] actions)         {          ... } 

and custom validate access attribute uses thinktecture

public class validateaccess : claimsauthorizeattribute     {         private static readonly ilog log = logmanager.getlogger(typeof(validateaccess));         private readonly string _resource;         private readonly string _claimsaction;          public validateaccess(string claimsaction, string resource)         {             _claimsaction = claimsaction;             _resource = resource;             xmlconfigurator.configure();         }          protected override bool isauthorized(httpactioncontext actioncontext)         {                         if (actioncontext == null) throw new argumentnullexception("actioncontext");             if (!httpcontext.current.user.identity.isauthenticated)             {                 log.infoformat("user {0} not authenticated - not authorizing further. redirecting error page.",                     httpcontext.current.user.identity.name);                  return false;             }              // specified users or roles when use our attribute             return checkaccess(actioncontext);         }          protected override bool checkaccess(httpactioncontext actioncontext)         {                         if (_claimsaction == string.empty && _resource == string.empty)             {                 //user in landing page                 return true;             }             return claimsauthorization.checkaccess(_claimsaction, _resource);         }     } 

my problems

• i not familiar web api. isauthorized(httpactioncontext actioncontext) right method override enforce access policy on api calls?

• why getting null user identity?