IN Operator between 2 collection objects

Question

In Sql, I know we have the IN operator and the equivalent of that is .Contains() in LINQ but i am stuck on one problem here

Consider the following linq query:

_dbContext.Offices.Where(o => o.Id == policy.OfficeId).FirstOrDefaultAsync()

Suppose i were to introduce a policies (plural) object which is a collection object each policy in the collection has its own officeId, how do I check if the offices collection consists of the officesId from policies collection object? I would like to do this in method syntax if possible. Thanks in advance.

Answer 1

Without having access to your data model, your answer does seem plausible; however, you need to have a call to .ToListAsync() at the end for this to compile. Also, it's more efficient to use Any() (rather than .Select.Contains):

await _dbContext.Offices.Where(o => policies.Any(p => p.OfficeId == o.Id)).ToListAsync();

I'm not sitting in front of a compiler, but if you just want the first one, the following is even better IIRC:

await _dbContext.Offices.FirstOrDefaultAsync(o => policies.Any(p => p.OfficeId == o.Id));