What is the linq equivalent to the SQL IN operator

Question

With linq I have to check if a value of a row is present in an array.
The equivalent of the sql query:

WHERE ID IN (2,3,4,5)

How can I

Answer 1

You can write help-method:

    public bool Contains(int x, params int[] set) {
        return set.Contains(x);
    }

and use short code:

    var resultset = from x in collection
                    where Contains(x, 2, 3, 4, 5)
                    select x;

Answer 2

.Contains

var resultset = from x in collection where new[] {2,3,4,5}.Contains(x) select x

Of course, with your simple problem, you could have something like:

var resultset = from x in collection where x >= 2 && x <= 5 select x

Answer 3

The above situations work when the Contains function is used against primitives, but what if you are dealing with objects (e.g. myListOrArrayOfObjs.Contains(efObj))?

I found a solution! Convert your efObj into a string, thats separated by _ for each field (you can almost think of it as a CSV representation of your obj)

An example of such may look like this:

     var reqAssetsDataStringRep = new List<string>();

        foreach (var ra in onDemandQueueJobRequest.RequestedAssets)
        {
            reqAssetsDataStringRep.Add(ra.RequestedAssetId + "_" + ra.ImageId);
        }

        var requestedAssets = await (from reqAsset in DbContext.RequestedAssets
                                     join image in DbContext.Images on reqAsset.ImageId equals image.Id
                                     where reqAssetsDataStringRep.Contains(reqAsset.Id + "_" + image.Id)
                                     select reqAsset
                                           ).ToListAsync();