Question

我正在尝试执行此Linq查询：

dataContext.Request.Where(x => x.LatestResponse.IsReviewRequired);

问题是LatestResponseID实际上不是Request表上的列。

要获得LatestResponse，我必须执行此操作SQL：

  SELECT ....
  FROM [doe].[Request] Req
      LEFT JOIN (
          SELECT MAX(ResponseID)
          FROM [doe].[Response]
          GROUP BY [RequestID]) AS Resp ON Req.[RequestID] = Resp.[RequestID]
      LEFT JOIN [doe].[Response] LatestResp ON Resp.[ResponseID] = LatestResp.[ResponseID]

我可以map吗？如果是这样，怎么样？

Answer 1

你可以这样做（如果你想要加入两边）：

var results = dataContext.Requests.Select(request => new
        {
            Request = request,
            LatestResponse = request .Responses.FirstOrDefault(response => response .RequestID == request.Responses.Max(response2 => response2.RequestID))
        });

此外，如果您尝试重新获取请求对象，但是通过最新响应的属性对其进行过滤，则以下是一个示例：

var results = dataContext.Requests.Select(request => new
        {
            Request = request,
            LatestResponse = request.Responses.FirstOrDefault(response => response.RequestID == request.Responses.Max(response2 => response2.RequestID))
        }).Where(request => request.LatestResponse.MyProperty == "Value").Select(request => request.Request);

EF映射对象列表中的最新对象

1 个答案: