Linq-to-Entities包含方法未找到 [英] Linq-to-Entities Include method not found

问题描述

我在MVC3应用程序中使用EF4，并且正在寻找一种方法来查看给定工作组中的所有联系人。在控制器中，我指定：

  var wg = from _ in _repo.Workgroups.Include（Contact）。ToList（） ; 
  

但是我收到以下错误：

'System.Linq.IQueryable'不包含'Include'的定义，并且没有扩展方法'Include'接受类型'System.Linq.IQueryable'的第一个参数可以找到（你是缺少使用指令或程序集引用？）

尽管这种方法内置于EF4中。我有没有启用它？

解决方案

是的方法是建立在EF中，但不能在 IQueryable 界面。它可以在 ObjectQuery 中找到。如果你想在 IQueryable 上调用它，你必须创建自己的扩展，将当前的查询转换为 ObjectQuery 并执行包含。如下所示：

  public static IQueryable< T>包含< T>（此IQueryable< T>查询，字符串属性）
 {
 var objectQuery = Query as ObjectQuery< T>; 
 if（objectQuery == null）
 {
抛出新的NotSupportedException（Include只能在ObjectQuery上调用）; 
} 
 
 return objectQuery.Include（property）; 
} 
  

或者你必须使用实体框架功能CTP5 ，其中此类扩展已经可用。

I am using EF4 within a MVC3 application and I was looking for a way to view all my contacts within a given workgroup. In the controller I specified:

var wg = from w in _repo.Workgroups.Include("Contact").ToList();

but I get the following error:

'System.Linq.IQueryable' does not contain a definition for 'Include' and no extension method 'Include' accepting a first argument of type 'System.Linq.IQueryable' could be found (are you missing a using directive or an assembly reference?)

I though this method was built into EF4. Do I have enable it somehow?

解决方案

Yes the method is build into EF but it is not available on IQueryable interface. It is available on ObjectQuery. If you want to call it on IQueryable you must create your own extension wich will convert current query to ObjectQuery and perform Include. Something like:

public static IQueryable<T> Include<T>(this IQueryable<T> query, string property)
{
  var objectQuery = query as ObjectQuery<T>;
  if (objectQuery == null)
  {
    throw new NotSupportedException("Include can be called only on ObjectQuery");
  }

  return objectQuery.Include(property);
}

Or you must use Entity Framework Feature CTP5 where such extensions are already available.

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