EntityFramework 4.5 - Still get ObjectDisposedException even after using Include

Question

I am facing the exception The ObjectContext instance has been disposed and can no longer be used for operations that require a connection even after using the Include method.

Here the function that retrieve the entities:

    public List<Entity.CapacityGrid> SelectByFormula(string strFormula, int iVersionId)
    {
        // declaration
        List<Entity.CapacityGrid> oList;

        // retrieve ingredients
        oList = (from Grid in _Dc.CapacityGrid.Include("EquipmentSection")
                             join Header in _Dc.CapacityHeader
                             on Grid.HeaderId equals Header.HeaderId
                             where Header.Formula == strFormula
                             && Header.VersionId == iVersionId
                             select Grid).ToList();

        // return
        return oList;

Here the usage of the function:

        // retrieve ingredient quantity by equipement
        using (Model.CapacityGrid oModel = new Model.CapacityGrid(Configuration.RemoteDatabase))
            oQuantity = oModel.SelectByFormula(strFormulaName, iVersionId);

        // code to throw the exception
        var o = (oQuantity[0].EquipmentSection.TypeId);

I understand that the using is closing the connection. I thought the ToList() will instantiated the list of objects and the related objects in the include before closing.

Can someone point me out what I do wrong? Sorry, my question was not clear. I do understand that including the line that throw exception inside the bracket of the using is working, but I do not figure out why does the include does not works?

Thank you!

Answer 1

Try changing

    // retrieve ingredient quantity by equipement
    using (Model.CapacityGrid oModel = new Model.CapacityGrid(Configuration.RemoteDatabase))
   {  // <-- **add these**
        oQuantity = oModel.SelectByFormula(strFormulaName, iVersionId);

    // code to throw the exception
    var o = (oQuantity[0].EquipmentSection.TypeId);
   } // <-- **add these**

Ref: http://msdn.microsoft.com/en-us/library/yh598w02.aspx

With no {} to englobe the using, the connection is disposed right after the first line. Because Entity framework uses Expression trees (this means that the request is not executed until it really needs it), your query happens at var o = (oQuantity[0].EquipmentSection.TypeId);.