C# Compare Two Lists of Different Objects [duplicate]

Answer 1

I would recommend converting the Ids of the 2 types to 2 HashSets. Then you can

HashSet a = new HashSet(firstList.Select(o => o.Id));

HashSet b = new HashSet(secondList.Select(o => o.Id));
if (a.IsSubsetOf(b) && b.IsSubsetOf(a))
{
    //Do your thing
}