c# - EntityFramework 4.5 - 即使在使用 Include 之后仍然会出现 ObjectDisposedException

Question

即使在使用 Include 方法后，我也遇到了异常ObjectContext 实例已被处置并且不能再用于需要连接的操作。

这里是检索实体的函数:

    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;

这里是函数的用法:

        // 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);

我知道 using 正在关闭连接。我认为 ToList() 将在关闭之前实例化包含的对象列表和相关对象。

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?

谢谢!

Answer 1

尝试改变

    // 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**

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

没有{}为了方便使用，连接被安排在第一行之后。因为 Entity Framework 使用表达式树(这意味着请求在真正需要它之前不会执行)，您的查询发生在 var o = (oQuantity[0].EquipmentSection.TypeId);。 .