Lazy loading not active for new added object

Question

I am using the unit of work with repository pattern in my ASP.NET project together with Entity Framework 6.

The problem I am facing is, is that when I add a new object to the database, its not directly active for Lazy loading when I call that same object again.

For example:

I have a Attendance object which contains 2 virtual links to DayCode and Employee.

public partial class Attendance
{
    public Attendance()
    {
        this.Id = -1;
        this.EmployeeId = -1;
        this.Present = false;
        this.Time = 0;
        this.Closed = false;
        this.Correction = false;
    }

    public int Id { get; set; }
    public int EmployeeId { get; set; }
    public bool Present { get; set; }
    public System.DateTime Date { get; set; }
    public string Remark { get; set; }
    public int Time { get; set; }
    public Nullable<short> DayCodeId { get; set; }
    public bool Closed { get; set; }
    public bool Correction { get; set; }

    public virtual Employee Employee { get; set; }
    public virtual DayCode DayCode { get; set; }
}

My DayCode class:

public partial class DayCode
{
    public DayCode()
    {
        this.Id = -1;
        this.Code = "";
        this.Attendances = new HashSet<Attendance>();
    }

    public short Id { get; set; }
    public string Code { get; set; }
    public string Title { get; set; }
    public string Color { get; set; }

    public virtual ICollection<Attendance> Attendances { get; set; }
}

My click event of a button on my webpage:

    protected void btnSaveCorrection_Click(object sender, EventArgs e)
    {
        Attendance attendance = GetItem();

        try
        {
            unitOfWork.AttendanceRepository.Add(attendance);
            unitOfWork.Save();
        }
        catch
        {
            ShowMessage("Problemen ondervonden, probeer opnieuw!", "alert alert-danger");
        }

        // Load attendances
        LoadAttendances(3); // Test Michael
        LoadCorrections(3); // Test Michael
    }

My LoadCorrections method:

    private void LoadCorrections(int employeeId) // Test _EmployeeId
    {
        //...

        Employee _employee = unitOfWork.EmployeeRepository.LoadItem(employeeId);

        int counter = 0;
        foreach (Attendance attendance in _employee.Attendances.Where(
                e => e.Correction && e.Date.Month == _Date.Month
            ).OrderBy(e => e.Date).ThenBy(e => e.Id))
        {
            _bodyRow = new BTableBodyRow();
            _bodyRow._CssClass = "";

            //...

            _cellBody = new BTableBodyCell();
            _cellBody._Content = attendance.DayCode.Code + " ( " + attendance.DayCode.Title + " )";

            //Here I get a nullreference exception!!!!!!!!!!!!!!!!!!

            _cellBody._CssClass = "left";
            _bodyRow._BodyCells.Add(_cellBody);

            //...

            _bodyRows.Add(_bodyRow);

            counter++;
        }

        //...
    }

Do I have to update in some of way the Lazy loading or... ?

Community · Accepted Answer · 2017-05-23 11:50:55Z

0

Found the solution reading the answer of Entity Framework Code First not lazy loading after save

The problem was that I only created a new instance of the POCO class and not the proxy. In my Repository pattern I created a new virtual method Create which creates this proxy.

public virtual T Create()
{
    return this._dbSet.Create<T>();
}

And instead of creating a new instance of the attendance class using:

Attendance attendance = new Attendance();

I use the Repository pattern method Create:

Attendance attendance = unitOfWork.AttendanceRepository.Create();

Now the null reference exception is gone.

edited May 23, 2017 at 11:50

CommunityBot

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answered Dec 7, 2014 at 15:52

Mivaweb

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