将此 SQL 语句转换为 LINQ

Question

我对 linq 很陌生，在 LINQ 中高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')))

有什么帮助吗？我已经尝试过以下解决方案：How would you do a "not in" query with LINQ?，但出现以下错误：无法创建类型为“TaskManager.Models.Task”的常量值。此上下文仅支持原始类型（“例如 Int32、String 和 Guid”）。

Answer 1

只是在我的脑海中做这件事，但也许是这个？

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
            };

Answer 2

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};