Question

Could someone explain how does Union in LINQ work?

It is told that it merges two sequences and removes duplicates.

But can I somehow customize the duplicate removal behavior – let’s say if I wish to use the element from the second sequence in case of duplicate or from the first sequence.

Or even if I wish to somehow combine those values in the resulting sequence?

How should that be implemented?

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Update

I guess I described the problem incorrectly, let’s say we have some value:

class Value {
   String name
   Int whatever;
}

and the comparer used performs a x.name == y.name check.

And let’s say that sometimes I know I should take the element from the second sequence, because it’s whatever field is newer / better than the whatever field of the first sequence.

Anyway, I would use the sequence1.Union(sequence2) or sequence2.Union(sequence1) variation of the methods.

Thank you

Answer 1

You can use second.Union(first) instead of first.Union(second). That way, it will keep the items from second rather than the items from first.