Remove duplicates of a List, selecting by a property value in C#?

Question

I have a list of objects that I need some duplicates removed from. We consider them duplicates if they have the same Id and prefer the one whose booleanValue is false. Here's what I have so far:

objects.GroupBy(x => x.Id).Select(x => x.Where(y => !y.booleanValue));

I've determined that GroupBy is doing no such grouping, so I don't see if any of the other functions are working. Any ideas on this? Thanks in advance.

Answer 1

You can do this:

var results = 
    from x in objects
    group x by x.Id into g
    select g.OrderBy(y => y.booleanValue).First();

For every Id it finds in objects, it will select the first element where booleanValue == false, or the the first one (if none of them have booleanValue == false).

If you prefer fluent syntax:

var results = objects.GroupBy(x => x.Id)
                     .Select(g => g.OrderBy(y => y.booleanValue).First());