Question

I am new to linq. So far I’ve been primarily using linqTOsql like this: MyRepository.Mytable.Where(x => x.id == 2).

I am wondering how to take a list from that type of query and put a specific parameter into a new simple list like List<long>.

So I get my records like this:

List<Entry2Cats> e2c = genesisRepository.Entry2Cats.Where( x => x.streamEntryID == id).ToList()

And I want to get the category ID paramter for each item in e2c so I can move it into a List<long>.

Obvisouly, this can be done fairly simply with a foreach:

        List<Entry2Cats> e2c = genesisRepository.Entry2Cats
                               .Where(x => x.streamEntryID == id)
                               .ToList();
        List<long> e2cCatIDs = new List<long>();

        foreach (Entry2Cats item in e2c)
        {
            e2cCatIDs.Add(item.catID);
        }

Can this be done using just linq? If it can, should I even bother with it or is the foreach just as good?

Answer 1

List<long> ids = genesisRepository.Entry2Cats
                 .Where(x => x.streamEntryID == id)
                 .Select(a => a.catID)
                 .ToList();

Just use Select to get only the IDs.