Asp.net mvc 在Entity Framework 6中急切加载时的多个DB查询

我的问题是，每次加载此视图时，我的应用程序都会向数据库发送249个相同的查询。最初我使用的是延迟加载，查询的数量是原来的两倍

上面的249数字表示此查询返回的行数

我的理解是.Include创建一个应该消除这种行为的联接

有人能告诉我如何消除这种重复的查询吗

干杯

下面的代码是伪代码，不用于编译

控制器：

 var apples = _unitOfWork.Context.Apples
    .Include(x=> x.AppleTypes)
    .OrderByDescending(x => x.Id)
    .Where(x => x.Status == (int)AppleStatusConstants.New 
          && x.IsRejected != true && x.AppleManId != null);

 return View(apples);

@model IEnumerable<Apple>

@Html.DisplayNameFor(model => model.AppleTypes.TypeSeason)
@foreach (var item in Model){
         @Html.DisplayFor(modelItem => item.AppleTypes.TypeSeason)
         }

    SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[Type] AS [Type],  
[Extent2].[Id] AS [Id1], 
[Extent2].[TypeSeason] AS [TypeSeason], 

FROM  [dbo].[Apples] AS [Extent1]
LEFT OUTER JOIN [dbo].[AppleTypes] AS [Extent2] ON [Extent1].[Id] = [Extent2].[Id]
WHERE (0 = [Extent1].[Status]) AND ( NOT ((1 = [Extent1].[IsRejected]) AND ([Extent1].[IsRejected] IS NOT NULL))) AND ([Extent1].[OrgUnitId] IS NOT NULL)
ORDER BY [Extent1].[Id] DESC

查看：

 var apples = _unitOfWork.Context.Apples
    .Include(x=> x.AppleTypes)
    .OrderByDescending(x => x.Id)
    .Where(x => x.Status == (int)AppleStatusConstants.New 
          && x.IsRejected != true && x.AppleManId != null);

 return View(apples);

@model IEnumerable<Apple>

@Html.DisplayNameFor(model => model.AppleTypes.TypeSeason)
@foreach (var item in Model){
         @Html.DisplayFor(modelItem => item.AppleTypes.TypeSeason)
         }

    SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[Type] AS [Type],  
[Extent2].[Id] AS [Id1], 
[Extent2].[TypeSeason] AS [TypeSeason], 

FROM  [dbo].[Apples] AS [Extent1]
LEFT OUTER JOIN [dbo].[AppleTypes] AS [Extent2] ON [Extent1].[Id] = [Extent2].[Id]
WHERE (0 = [Extent1].[Status]) AND ( NOT ((1 = [Extent1].[IsRejected]) AND ([Extent1].[IsRejected] IS NOT NULL))) AND ([Extent1].[OrgUnitId] IS NOT NULL)
ORDER BY [Extent1].[Id] DESC

一瞥截图

在Entity Framework 6中急切加载时的多个DB查询

您没有告诉它立即加载基本查询，只告诉它包含

此代码：

var apples = _unitOfWork.Context.Apples
  .Include(x=> x.AppleTypes)
  .OrderByDescending(x => x.Id)
  .Where(x => x.Status == (int)AppleStatusConstants.New 
         && x.IsRejected != true && x.AppleManId != null);

正在创建一个

IQueryable

。简单的解决方案是在末尾添加

.ToList（）

  .Where(x => x.Status == (int)AppleStatusConstants.New 
     && x.IsRejected != true && x.AppleManId != null)
  .ToList(); 

因此，在您的代码中，这是罪魁祸首：

@foreach (var item in Model){

这将导致EF一次查询一个实体

PS：以下语句是相同的（除非您重写了object.cshtml）

及

及

---

.ToList（）是一个更昂贵的操作吗？这里的一位高级程序员鼓励我尽可能不要使用.ToList（）。这不是一个好答案。这要看情况而定。有时

.ToList（）

是正确的解决方案，有时则不是。