protected override StudentDTO CreateEntity([FromBody]StudentDTO entityDto)
{
    if (ModelState.IsValid)
    {
        var entity = entityDto.ToEntity();
        _context.Students.Add(entity);
        _context.SaveChanges();
        return new StudentDTO(_context.Students
            .Include(p => p.ID_RoomForeignKey)
            .Include(s => s.ID_UserNumber)
            .FirstOrDefault(p => p.ID_Student == entity.ID_Student));
    }
    else
    {
        HttpResponseMessage response = null;
        //response = Request.CreateResponse(HttpStatusCode.BadRequest, new ODataError
        //{
        //    ErrorCode = "ValidationError",
        //    Message = String.Join(";", ModelState.Values.First().Errors.Select(e => e.ErrorMessage).ToArray())

        //});
        throw new HttpResponseException(response);
    }
}

public class Student
{
    [Key]
    public int ID_Student { get; set; }

    [Required]
    [StringLength(500)]
    public string FIOStudent { get; set; }
    public DateTime BirthDate { get; set; }
    [Required]
    [StringLength(500)]
    public string Faculty { get; set; }
    [Required]
    [StringLength(500)]
    public string Group { get; set; }
    [Required]
    [StringLength(500)]
    public string EducationalForm { get; set; }
    public int ID_Room { get; set; }
    public int id_user { get; set; }
    public virtual Room ID_RoomForeignKey { get; set; }
    public virtual User ID_UserNumber { get; set; }

}

public class StudentDTO
{
    public StudentDTO() {

    }
    public StudentDTO(Student student)
    {
        ID_Student = student.ID_Student;
        FIOStudent = student.FIOStudent;
        BirthDate = student.BirthDate;
        Faculty = student.Faculty;
        Group = student.Group;
        EducationalForm = student.EducationalForm;
        ID_Room = student.ID_Room;
        TypeRoom = student.ID_RoomForeignKey.TypeRoom;
        Floor = student.ID_RoomForeignKey.Floor;
        user_id = student.ID_UserNumber.user_id;
        Login = student.ID_UserNumber.Login;
        Password = student.ID_UserNumber.Password;

    }
    [Key]
    public int ID_Student { get; set; }

    [Required]
    [StringLength(500)]
    public string FIOStudent { get; set; }
    public DateTime BirthDate { get; set; }
    [Required]
    [StringLength(500)]
    public string Faculty { get; set; }
    [Required]
    [StringLength(500)]
    public string Group { get; set; }
    [Required]
    [StringLength(500)]
    public string EducationalForm { get; set; }
    public int ID_Room { get; set; }
   //public int id_user { get; set; }
   //public int ID_Room { get; set; }
    public string TypeRoom { get; set; }
    public int Floor { get; set; }

    public int user_id { get; set; }
    [Required]
    [StringLength(500)]
    public string Password { get; set; }
    [Required]
    [StringLength(500)]
    public string Login { get; set; }

    public Student ToEntity()
    {
        return new Student
        {
            ID_Student = ID_Student,
            FIOStudent = FIOStudent,
            BirthDate = BirthDate,
            Faculty = Faculty,
            Group = Group,
            EducationalForm = EducationalForm,
            ID_Room = ID_Room,
            id_user = user_id

        };
    }
}

<div id="createBlock"  float="right" display="inline-block" margin="20px">
    <h3>Добавление </h3>
    <table>
        <tr><td><label>ФИО: </label></td><td><input type="text" id="editFIO" /></td></tr>
        <tr><td><label>Дата Рождения: </label></td><td><input type="text" id="editBirthDate" /></td></tr>
        <tr><td><label>Факультет: </label></td><td><input type="text" id="editFaculty" /></td></tr>
        <tr><td><label>Группа: </label></td><td><input type="text" id="editGroup" /></td></tr>
        <tr><td><label>Форма обучения: </label></td><td><input type="text" id="editEduForm" /></td></tr>
        <tr><td><label>Номер комнаты: </label></td><td><input type="number" id="editNumberRoom" /></td></tr>
    </table>
    <button id="addStudent">Сохранить</button>
</div>

<script type="text/javascript">
    $(document).ready(function () {

        GetAllStudents();

        $("#addStudent").click(function (event) {
            event.preventDefault();
            AddStudent();
        });

    });

    function AddStudent() {

        var student = {
            ID_Student: $('#editId').val(),
            FIOStudent: $('#editFIO').val(),
            BirthDate: $('#editBirthDate').val(),
            Faculty: $('#editFaculty').val(),
            Group: $('#editGroup').val(),
            EducationalForm: $('#editEduForm').val(),
            ID_Room: $('#editNumberRoom').val()
        };

        $.ajax({
            url: '/odata/Student',
            type: 'POST',
            data: JSON.stringify(student),
            contentType: "application/json;charset=utf-8",
            success: function (data) {
                GetAllStudents();
            },
            error: function (x, y, z) {
                alert(x + 'n' + y + 'n' + z);
            }
        });
    }
    function GetAllStudents() {

        $("#createBlock").css('display', 'block');
        $.ajax({
            url: '/odata/Student',
            type: 'Get',
            dataType: 'JSON',
            contentType: "application/json;charset=utf-8",
            async: false,
            success: function (data) {
                WriteResponse(data.value);
            },
            error: function (x, y, z) {
                alert(x + 'n' + y + 'n' + z);
            }
        });
    }
</script>

ODataModelBuilder modelBuilder = new ODataConventionModelBuilder();
modelBuilder.EntitySet<Student>("Student");
modelBuilder.EntitySet<StudentDTO>("StudentDTO");

modelBuilder.EntitySet<StudentDTO>("Student");