LINQ到SQL SELECT DISTINCT按多列，并返回整个实体 [英] LINQ to SQL Select Distinct by Multiple Columns and return entire entity

问题描述

我正与第三方数据库和需要选择一组数据为特定的市场，我寻找到了截然不同的。该数据是相同的每个市场，所以它是多余的上拉这一切，我不想为C周围没有任何逻辑很难$ C $，因为我们正在与供应商来解决这个问题，但我们需要一个修复程序将与供应商的解决以及方式的数据库，目前，因为它可以thier修复前一段时间去住。

I am working with a third party database and need to select a distinct set of data for the specific market that I am looking into. The data is the same for each market, so it is redundant to pull it all in, and I don't want to hardcode any logic around it as we are working with the vendor to fix the issue, but we need a fix that will work with the vendors fix as well as the way the database is currently as it could be some time before thier fix goes live.

我不被任何东西要分组，因为我想要得到的数据在最低水平，但我不希望任何冗余数据。我现在的查询类似于这样...

I do not want to group by anything as I want to get the data at the lowest level, but I don't want any redundant data. My current query looks similar to this...

determinantData = (from x in dbContext.Datas
                   where x.Bar.Name.Equals(barName) &&
                         x.Something.Name.Equals(someName) &&
                         FooIds.Contains(x.Foo.Id) &&
                         x.Date >= startDate && 
                         x.Date <= endDate
                   select x).Distinct();

这并没有做什么，我所期望的。我想通过三个属性来选择不同的记载，说富，酒吧和东西，但返回的整个对象。我怎样才能做到这一点使用LINQ？

This does not do what I expect. I would like to select the distinct records by three properties, say Foo, Bar, and Something but return the entire object. How can I do this using LINQ?

推荐答案

您可以使用按与你想成为独特的属性，然后选择第一项各组：

You could use group by with the properties that you want to be distinct, then select the first item of each group:

determinantData = (from x in dbContext.Datas
                   where x.Bar.Name.Equals(barName) &&
                         x.Something.Name.Equals(someName) &&
                         FooIds.Contains(x.Foo.Id) &&
                         x.Date >= startDate && 
                         x.Date <= endDate
                   group x by new { x.Foo, x.Bar, x.Something } into market 
                   select market).Select( g=> g.First()); 

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