Linq to 实体子查询

Question

如何在 Linq 中编写以下子查询：

Context.Set<Process>()
       .Include(...)
       .Where(x => x.Activity.Name.CompareTo(Context.Set<Activity>().Where(a => a.Id == activityId).Select(c => a.Name)) > 0)
       .Take(1);

这是一个简化版本的查询，WHERE 子句只包括不起作用的部分。如果我将 Context.Set().... 子查询更改为字符串常量，则查询有效。事实上，它给出了 NotSupportedException

LINQ to entities does not recognize method Set<Activity>

Answer 1

试试这个：

(from p in context.Set<Process>().Include(...)
 from a in context.Set<Activity>()
 where a.Id == activityId
 where p.Activity.Name.CompareTo(a.Name) > 0
 select p).Take(1);

Linq to 实体子查询

Linq to entities subquery

linq-to-entities

entity-framework

entity-framework-6