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我有 MVC Web 应用程序项目，我想要延迟加载。

我在导航属性中的模型对象中使用virtual了关键字，但我想在getmanualylist()我的存储库层中调用它的一种方法。我可以通过方法获取该对象的相关对象include。

我在许多网站中看到导航字段所在的位置virtual，它们可以include在一段代码中使用来预先加载对象，但我不能，因为当我在查询中运行我的方法时，我看到它返回了正确的查询。但是当我想查看列表时，它会返回null相关对象，它显示急切加载不起作用。

我不知道为什么会出现这个问题以及出了什么问题？

public IQueryable<InvoiceItem> GetManuallylist()
{
    IQueryable<InvoiceItem> query = null;
    query = this.dbContext.Set<InvoiceItem>().Include("PartLocation1").Include("PartContractInfo1");
    var list = this.dbContext.Set<InvoiceItem>().Include("PartContractInfo1").ToList();
    var list2 = this.dbContext.Set<InvoiceItem>().Include("PartLocation1").ToList();
    var list23 = this.dbContext.Set<InvoiceItem>().Include("PartBooklet2").ToList();
    return query;
}

这是我的 InvoiceItemModel 的一段代码

public virtual Invoice Invoice1 { get; set; } //  Invoice - 
public virtual SparePart SparePart2 { get; set; } //  SparePart - 
public virtual PartBooklet PartBooklet2 { get; set; } //  PartBooklet
public virtual PartLocation PartLocation1 { get; set; } //  PartLocation - 
public virtual PartContractInfo PartContractInfo1 { get; set; } //  ContractInfo - 
public virtual Project Project1 { get; set; } // Project
public virtual BaseData BaseData1 { get; set; }
public virtual BaseData BaseDataTakingplace { get; set; }
public virtual Personel PersonelTroubleshooter { get; set; }
public virtual Personel PersonelMasterApplier { get; set; }
public virtual Personel PersonelBuildingExpert { get; set; }

这是查询：

{SELECT 
[Extent1].[id] AS [id], 
[Extent1].[invoice] AS [invoice], 
[Extent1].[part_code] AS [part_code], 
[Extent1].[spare_part] AS [spare_part], 
[Extent1].[ProjectId] AS [ProjectId], 
[Extent1].[part_count] AS [part_count], 
[Extent1].[deliveris_partcount] AS [deliveris_partcount], 
[Extent1].[descr] AS [descr], 
[Extent1].[part_location] AS [part_location], 
[Extent1].[contract_info] AS [contract_info], 
[Extent1].[HasSerial] AS [HasSerial], 
[Extent1].[HasUselesSpiece] AS [HasUselesSpiece], 
[Extent1].[HasQCConfirmation] AS [HasQCConfirmation], 
[Extent1].[HasRepair] AS [HasRepair], 
[Extent1].[faulty_Reason] AS [faulty_Reason], 
[Extent1].[Troubleshooter] AS [Troubleshooter], 
[Extent1].[MasterApplier] AS [MasterApplier], 
[Extent1].[BuildingExpert] AS [BuildingExpert], 
[Extent1].[Takingplace] AS [Takingplace], 
[Extent1].[Warrantyperiod] AS [Warrantyperiod], 
[Extent1].[DeliveryDateForBuilding] AS [DeliveryDateForBuilding], 
[Extent2].[id] AS [id1], 
[Extent2].[train] AS [train], 
[Extent2].[wagon_number] AS [wagon_number], 
[Extent2].[install_date] AS [install_date], 
[Extent2].[pickup_date] AS [pickup_date], 
[Extent2].[descr] AS [descr1], 
[Extent3].[id] AS [id2], 
[Extent3].[contract] AS [contract], 
[Extent3].[project] AS [project], 
[Extent3].[contractor] AS [contractor], 
[Extent3].[SupplierId] AS [SupplierId], 
[Extent3].[SupplyType] AS [SupplyType], 
[Extent3].[request] AS [request], 
[Extent3].[request_date] AS [request_date], 
[Extent3].[SparePartStatusValue] AS [SparePartStatusValue], 
[Extent3].[unit_price] AS [unit_price], 
[Extent3].[total_cost] AS [total_cost], 
[Extent3].[descr] AS [descr2], 
[Extent3].[BaseData_Id] AS [BaseData_Id]
FROM   [dbo].[invoice_item] AS [Extent1]
LEFT OUTER JOIN [dbo].[part_location] AS [Extent2] ON [Extent1].[part_location] = [Extent2].[id]
LEFT OUTER JOIN [dbo].[part_contract_info] AS [Extent3] ON [Extent1].[contract_info] = [Extent3].[id]}
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