Linq和三表分组

我提出了以下LINQ，但我忍不住想，我应该能够在一个查询而不是两个查询中完成这项工作。有人能帮忙吗

其思想是将三个表内部连接起来，然后逐个分组

var q1 = from er in ExportRules
    join per in PlaceExportRules on er.ExportRulesID equals per.ExportRulesID
    select new 
    {
        PlaceID = per.PlaceID, 
        Description = er.Description, 
        Tag = er.TagName,
        ExportName = per.ExportName,
        ExportAddress = per.ExportAddress
    };

var q2 = from p in Places 
    join rules in q1 on p.PlaceID equals rules.PlaceID into joined2
    where joined2.Any()
    orderby p.PlaceName
    select new {Place = new {p.PlaceID, p.PlaceName}, joined2};

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好吧，你可以把一些东西括起来：

var query = from p in Places
            join rules from 
                 (from er in ExportRules
                  join per in PlaceExportRules 
                    on er.ExportRulesID equals per.ExportRulesID
                  ...)
              on p.PlaceId equals rules.PlaceId into joined2
            where joined2.Any()
            orderby p.PlaceName
            select new {Place = new {p.PlaceID, p.PlaceName}, joined2};

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然而，我个人可能会把它作为两个问题。更清晰，不会影响性能-这不像代码中的第一条语句实际执行查询。

您不需要在一个查询中执行查询，所有查询都只执行一次（当您尝试通过ToList获取数据时，隐式地将其转换为一个查询，…）。谢谢@jonskeet，我就这样做了。