如何翻译为 Linq 表达式答案

【问题标题】：How to translate to Linq Expression如何翻译为 Linq 表达式
【发布时间】：2013-06-05 17:59:38
【问题描述】：

我有以下无法翻译成 linq 的 sql 命令

select Distinct(fp.Parks_Id)
from ParkFeaturePark fp
Inner Join Parkfeatures feat on fp.ParkFeatures_Id = feat.Id
Inner Join Parks p On fp.Parks_Id = p.Id
where  p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =1 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =2 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =31     )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =42 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =106 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =118 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =4 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =6 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =10 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =18 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =22 )
    And p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =46 )

这里的转折是..我必须使用用户选择的组合..示例是

    p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =1 )
    AND p.Id In (Select Parks_Id from ParkFeaturePark where ParkFeatures_Id =4 )

或用户选择的任何其他组合..

感谢回复

【问题讨论】：

标签： sql linq lambda sql-to-linq-conversion

【解决方案1】：

假设您有导航属性Park.ParkFeatureParks 和ParkFeaturePark.Parkfeatures。（否则将能够创建它们）。然后你可以这样做：

int[] featureIds = new { 1, 2, 31, 42, 106, 118, .. };

var query = from p in context.Parks
            where p.ParkFeatureParks
                   .SelectMany(pfp => pfp.Parkfeatures)
                   .All(feature => featureIds
                                   .Contains(id => feature.ParkFeatures_Id))
            select p.Parks_Id;

【讨论】：

感谢 Gert，但我的问题是，我想获取那些将所有 featureId 传递给它的 Park_id，比如...我想要那些具有 1、2、10 featureId 的 ID。而不是那些只有 1 和 2 个 featureId 的公园。对不起我的英语不好。希望你明白我的意思。

【解决方案2】：

这不是答案，而是好的风格编码 -

SELECT DISTINCT(fp.Parks_Id)
FROM dbo.ParkFeaturePark fp
JOIN dbo.Parkfeatures feat ON fp.ParkFeatures_Id = feat.Id
JOIN dbo.Parks p ON fp.Parks_Id = p.Id
WHERE p.Id IN (
        SELECT Parks_Id 
        FROM dbo.ParkFeaturePark 
        WHERE ParkFeatures_Id IN (1, 2, 31, 42, 106, 118, 4, 6, 10, 18, 22, 46)
    )

【讨论】：

感谢 devart，不知怎的给了我一个想法
我正在考虑使用 Predicate Builder 使“where”动态化.. 但是不使用它可以做到吗？