Get distinct values of List in List

问题

I'm struggling with a db application, where I need to get the distinct values. The whole structure looks somewhat like this

class A
{
    public virtual ICollection<B> Bs { get; set; }
}
class B
{
    public virtual C C { get; set; }
}
class C
{
    public int x {get; set;}
}

This is the model from a db and I have a subset of all A's. Now I need to get all distinct values C.x from all those A's. So basically something like

db.A.Where(something).SelectMany(s => s.Bs.SelectMany(t => t.C.x).ToList().Distinct()).ToList()

But it tells me, that the second SelectMany cannot be inferred from the usage.

回答1:

Fix your code like this:

SelectMany(s => s.Bs.Select(t => t.C.x)

Note that B is not a member of A but Bs, and also your second SelectMany should be Select.

Read more https://stackoverflow.com/a/25564528/2946329

回答2:

Could you try this? Also I think it'll be needed to add .Include statements:

db.A.Where(something)/*.Include(a => a.Bs.Select(b => b.C))*/
    .SelectMany(x => x.Bs.Select(b => b.C.x)).Distinct();

来源：https://stackoverflow.com/questions/47221090/get-distinct-values-of-list-in-list