How can i post a list object to API by using Checkbox and Angularjs?

My problem is:
I have a list Student in a table with checkbox. Now i want to check this box and send a list Student to API. But i cannot to get them.
My code here!


<tr dir-paginate="student in ClassStudents | filter: search | itemsPerPage: 20">
    <td><input type="checkbox" ng-model="student.selected"></td>
    <td style="display: none;">{{student.Class.ClassId}}</td>
    <td>[Another property]</td>


function selectStudents(){
    var listStudent = [];
        var studentClone = angular.copy(student);
    return listStudent;
$scope.upGrade = function(){
        method: 'POST',
        url: host + "/api/APIClassStudents/Post",
        data: {
            Students: selectStudents(),
            ClassId: 2
        alert("Upgrade Successful!")

Connect to WEB API is ok, response Upgrade success! but nothing change. When i debugging, i think selectStudent()[now is a array] is count = 0. And i dont know why.
Thanks for help!

Source: AngularJS