What is the linq equivalent to the SQL IN operator

.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

Perform the equivalent of an SQL IN with IEnumerable.Contains().

var idlist = new int[] { 2, 3, 4, 5 };

var result = from x in source
          where idlist.Contains(x.Id)
          select x;

db.SomeTable.Where(x => new[] {2,3,4,5}.Contains(x));

or

from x in db.SomeTable
where new[] {2,3,4,5}.Contains(x)

An IEnumerable<T>.Contains(T) statement should do what you're looking for.

A very basic example using .Contains()

List<int> list = new List<int>();
for (int k = 1; k < 10; k++)
{
    list.Add(k);
}

int[] conditionList = new int[]{2,3,4};

var a = (from test in list
         where conditionList.Contains(test)
         select test);

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();

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;