将此SQL语句转换为LINQ

Question

我对linq很陌生，我在LINQ中有效地编写此查询时遇到了一些困难。

SELECT ID, UniqueID, RouteHeaderID, RouteObjectState, OriginalRouteUniqueID 
FROM dbo.MeterReadingOrderERPRouteCreateResponses 
WHERE (ID NOT IN (SELECT MeterReadingOrderERPRouteCreateResponseID 
        FROM dbo.Tasks 
        WHERE (TaskType = 'MeterReading'))) 

请帮忙吗？我试过这个解决方案：How would you do a "not in" query with LINQ?，但出现以下错误：无法创建类型'TaskManager.Models.Task'的常量值。在此上下文中仅支持基本类型（如Int32，String和Guid）。

Answer 1

var meterReadingTasks = from task in context.Tasks 
         where task.TaskType == "MeterReading" 
         select task.MeterReadingOrderERPRouteCreateResponseID; 

var results = from m in context.MeterReadingOrderERPRouteCreateResponses 
       where !meterReadingTasks.Contains(m.Id) 
       select new { m.ID, m.UniqueID, m.RouteHeaderID, m.RouteObjectState, m.OriginalRouteUniqueID}; 

Answer 2

只是这样做了我的头顶，但也许这？

var subQuery = from t in Tasks 
       where t.TaskType == "MeterReading" 
       select t.MeterReadingOrderERPRouteCreateResponseID 

var query = from m in MeterReadingOrderERPRouteCreateResponses 
      where !subQuery.Contains(m.ID) 
      select new 
      { 
       ID = m.ID, 
       UniqueID = m.UniqueID, 
       RouteHeaderID = m.RouteHeaderID, 
       RouteObjectState = m.RouteObjectState, 
       OriginalRouteUniqueID = m.OriginalRouteUniqueID 
      };