[ASP.NET Core+AngularJS] Controller gets NULL value

Question

I am using VS2015. I am getting error in my controller class (System.NullReferenceException) but in my angularjs I get the value 

{"UserName":"admin","UserPassword":"password"}

Hoping you can help me on this. Thanks in Advance. 

 

Below is my controller class:

 

[HttpPost]
public JsonResult AuthenticateUser(UserAccessViewModel _users)
{

     var users = _context.UserAccess.Where(w => w.Username.Equals(_users.UserName) &&                    w.Userpassword.Equals(_users.UserPassword));

     return Json(users);
}

 Controller.js

app.controller("MyController", function ($scope, MyService) {

    $scope.LoginCheck = function () {

        $scope.userlogin = {
            UserName: $scope.usrName,
            UserPassword: $scope.usrPassword
        }

        var getData = CartExpressService.UserLogin($scope.UserAccessViewModel);
        getData.then(function (d) {
            $scope.msg = d.data;
            alert($scope.msg);

        });
        debugger;
    }


});

 Service.js

app.service("MyService", function ($http) {

    this.UserLogin = function (user) {

        var response = $http({
            method: "post",
            url: "../Administrator/AuthenticateUser",
            data: JSON.stringify(user),
            dataType: "json"
        });

        return response;
    }
});

Views

    <div style="margin-bottom: 25px" class="input-group">
        <span class="input-group-addon"><i class="glyphicon glyphicon-user">i>span>
        <input type="text" class="form-control" ng-model="UserAccessViewModel.UserName" placeholder="Username">
    div>

    <div style="margin-bottom: 25px" class="input-group">
        <span class="input-group-addon"><i class="glyphicon glyphicon-lock">i>span>
        <input type="password" class="form-control" ng-model="UserAccessViewModel.UserPassword"  placeholder="Password">
    div>

    <div style="margin-top:10px" class="form-group">

        <div class="col-sm-12 controls">
            <a id="btn-login" href="#" class="btn btn-success" ng-click="LoginCheck()">Login  a>
        div>
    div>

form>

 

 Error: