$http.post can not send object to controller WebAPi

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Javascript

C#5.0

WebAPI

AngularJs

Hi all,
i am learning Angularjs . i have a code:
controller.js

$scope.save = function (position) {
           $http.post(serviceBase + 'Positions', { model: $scope.position })
              .success(function (data) {
                            });

$scope.position already returns an object {Name: "Name",Description:"Description"{
In api:

[HttpPost]
public HttpResponseMessage Post(Position model)
{
}

But in api i can not get model . It's properties are null.
Pls help me in this code. Thanks.
I already have tried :

$http.post(serviceBase + 'Positions', $scope.position) 

But it is same.