如何在linq的where子句中使用Contains [英] how to use Contains in where clause in linq

问题描述

我有这个:

        var myResult = uow.GetRepository<SLItemsCustomersCard, long>()
            .Query(x => x.CustomerId == customerId && x.SquareColor == squareColor)
            .OrderBy(x => x.BranchMapRang)
            .Select((r, i) => new { Row = r, Index = i })
            .Where(x => x.Index == visitCounter - 1).ToList();

但是我想在where子句中实现这一点:

but I want to achive this in where clause:

.Where(x => x.Index.Cotains(visitCounter)).ToList();

该怎么做?

推荐答案

您似乎误解了Contains方法的作用.我将此答案基于您之前的用法:

You seem to be misunderstanding what the Contains method does. I'm basing this answer on your earlier usage of:

Where(x => x.Index == visitCounter - 1)

换句话说，visitCounter是整数(Index也是).但是然后您要像这样使用它:

In other words, visitCounter is an integer (and so is Index). But then you want to use it like this:

Where(x => x.Index.Contains(visitCounter))

这在语法上没有意义.整数(Index)没有Contains函数.对我来说，您要达到的目标尚不完全清楚，但您的评论进一步阐明了这一点:

Which does not make syntactical sense. An integer (Index) does not have a Contains function. It's not fully clear to me what you are trying to achieve, but your comment clarifies it a bit more:

但是我想在SQL Server中实现类似IN子句的功能.

But I want to achieve something like IN clause in SQL server.

SQL中的IN子句需要一定范围的可能性(对于您的情况，为整数列表)，并且您在此处不使用整数列表.此外，您将其用Index.Contains(visitCounter)表示，这意味着您希望Index是整数列表?

The IN clause in SQL requires a range of possibilities (a list of integers, in your case), and you're not working with a list of integers here. Furthermore, you have phrased it as Index.Contains(visitCounter) which would imply that you're expecting Index to be the list of integers?

那根本没有道理.因此，假设您对伪代码不正确，我将为您提供最有意义的答案:

That simply doesn't make sense. So I'll give you the answer that makes the most sense, on the assumption that you weren't accurate with your pseudocode:

List<int> visitorIds = new List<int>() { 1, 5, 99, 125 };

然后您可以执行以下操作:

And then you can do the following:

.Where(x => visitorIds.Contains(x.Index))

简而言之，该代码段告诉计算机仅给出在visitorIds列表中提到Index的项目".

To put it in words, this snippet basically tells the computer to "only give the items whose Index is mentioned in the visitorIds list".

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