Linq GroupBy with each null value as a group

Question

I have an object with a nullable int property \"GroupId\".

With a List of this object, I would like to do a GroupBy on this \"GroupId\". But if I do it, all the null val

Answer 1

Generic Comparer that can be used without boxing.

public class NullableComparer : IEqualityComparer
        where T : struct
{
    public bool Equals(T? x, T? y)
    {
        if (x == null || y == null)
        {
            return false;
        }

        return x.Equals(y);
    }

    public int GetHashCode(T? obj)
    {
        return obj.GetHashCode();
    }
}

You would then use it like:

// where GroupId as a nullable Guid 
var grouped = MyList.GroupBy(f => f.GroupId, new NullableComparer());