Is there an AddUnique method similar to Addrange() for alist in C#

Question

I have a list in C#:

       var list = new List();
       list.AddRange(GetGreenCars());
       list.AddRange(GetBigCars());
       list.AddRange(         


        

Answer 1

I created an extension method that adds only unique values to anything implementing ICollection (including a List) from an IEnumerable. Unlike implementations that use List.Contains(), this method allows you to specify a lambda expression that determines if two items are the same.

/// 

/// Adds only items that do not exist in source.  May be very slow for large collections and some types of source.
/// 
/// Type in the collection.
/// Source collection
/// Predicate to determine whether a new item is already in source.
/// New items.
public static void AddUniqueBy(this ICollection source, Func predicate, IEnumerable items)
{
    foreach (T item in items)
    {
        bool existsInSource = source.Where(s => predicate(s, item)).Any();
        if (!existsInSource) source.Add(item);
    }
}

Usage:

source.AddUniqueBy((s, i) => s.Id == i.Id, items);