linq对实体不认识的方法 [英] linq to entities does not recognize the method

问题描述

我有一个存储库类，它有一个返回ObjectSet的方法

I have a repository class that has a method to return ObjectSet

像

public class Repository:ObjectContext
{
  public IObjectSet<T> GetObjectSet()
  {...}
}

当我使用在一个查询中，我得到linq到实体错误（不认识方法...）

When I use this in a query I get linq to entities error ( does not recognize method...)

我喜欢这样的想法，有一个通用存储库，每次都不会重新生成（与T4模板）
有没有办法扩展查询提供程序来识别我的方法？但是我想在服务器上解决它（换句话说就是参与查询生成）。
使用它的示例代码是：

I like this idea of having a generic repository which doesn't get regenerated every time (with T4 templates) Is there a way to extend the query provider to recognize my method ? But I do want to resolve it on server ( in other words participate in query generation). Sample code that uses it is:

static readonly Func<Repository,
        string, AuthorizedUser>  getInstitutionByAuthorizedUserName = CompiledQuery.Compile(
          (ObjectContext ctx, string userName) =>
              (from inst in ctx.GetObjectSet<Institution>()
              join auths in ctx.GetObjectSet<AuthorizedUser>() 
              on inst.Key equals auths.Institution.Key
              where auths.Name == userName
              select inst.Key).SingleOrDefault();

推荐答案

不要重新发明 CreateObjectSet 和 break the join 习惯：

Don't reinvent CreateObjectSet and break the join habit:

static readonly Func<Repository,
    string, AuthorizedUser>  getInstitutionByAuthorizedUserName = CompiledQuery.Compile(
      (ObjectContext ctx, string userName) =>
          from inst in ctx.CreateObjectSet<Institution>()
          from auths in inst.Authorizations
          where auths.Name == userName
          select inst.Key).SingleOrDefault();
       );

这篇关于linq对实体不认识的方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！