如何在实体框架中查询与ID数组的多对多关系

Question

Say there are stores, customers, and credit accounts. So customers and stores have a many-to-many relationship through the credit account table.

If I want every customer that has an account at a given store, I could access it like follows.

var customers = dbContext.Customers
    .Where(c => c.CreditAccounts.Select(a => a.StoreID).Contains(storeID));

That seems to work but when I want to search by multiple storeIds, I get an empty result set. Here are some things I've tried.

var customers = dbContext.Customers
    .Where(c => c.CreditAccounts.Any(a => storeIDs.Contains(a.StoreID)));

And

var customers = dbContext.Customers
    .Where(c => c.CreditAccounts.Select(a => a.StoreID).Intersect(storeIDs).Count() > 0);

These always give me empty results. How can I achieve this without writing a raw SQL query?

Update

I did not have the data that I thought I had. Once that was corrected, my queries began to work. I think the question is still valid though because it's not clear whether any of these perform well, so other users might wish to respond with the most efficient way to retrieve the results.

Answer 1

The following linq query will return the results that you are looking for - however, I am not certain that it will perform well at all:

var results = dbContext.Customers
    .Where(c => c.CreditAccounts.Join(storeIds.ToList(), a => a.StoreId, s => s, (a,s)=>s).Any());

You may get better performance by finding the credit accounts that intersect with the StoreID, and then joining the list of credit accounts with the customers table - although I can't tell from the code you have provided whether you have direct access to a list of creditaccounts.