c# - how to use Contains in where clause in linq

Question

I have this:

        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();

but I want to achive this in where clause:

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

How to do this?

Answer 1

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)

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))

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:

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

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?

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 };

And then you can do the following:

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

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