IEqualityComparer not working as intended

Question

I have a List of paths of files stored on my computer. My aim is to first filter out the files which have the same name and and then filter out those which have

Answer 1

Change your GetHashCode to work on the compared value. I.e. for your size comparer:

public int GetHashCode(string obj)
{
    return FileInfo(x).Length.GetHashCode();
}

And for the other:

public int GetHashCode(string obj)
{
    return Path.GetFileName(obj).GetHashCode();
}

According to this answer - What's the role of GetHashCode in the IEqualityComparer in .NET?, the hash code is evaluated first. Equals is called in case of collision.

Obviously it would be sensible to work on FileInfos, not on strings.

So maybe:

FileList.Select(x => new FileInfo(x))
        .Distinct(new CustomTextComparer())
        .Distinct(new CustomSizeComparer());

Of course, then you have to change your comparers to work on the correct type.