linq distinct c# example

Example 1: C# .NET Core linq Distinct

var distinctUsers = allUsers
    .GroupBy(x => x.UserId)
    .Select(x => x.First())
    .ToList();

Example 2: c# distinct comparer multiple properties

public static IEnumerable DistinctBy
    (this IEnumerable source, Func keySelector)
{
    HashSet seenKeys = new HashSet();
    foreach (TSource element in source)
    {
        if (seenKeys.Add(keySelector(element)))
        {
            yield return element;
        }
    }
}