Using LINQ to find duplicates (List extension)

gistfile1.cs

/// <summary>
/// Method that returns all the duplicates in the collection.
/// </summary>
/// <typeparam name="T">The type.</typeparam>
/// <param name="list">The Original List to detect for duplicates.</param>
/// <returns>A list of duplicates found in the Original List.</returns>
public static List<T> GetDuplicates<T>(this List<T> list)
{
    // Finding duplicates by Grouping the entries and then finding 
    // Groups that have more than one entity
    var duplicateList = list.GroupBy(i => i).Where(j => j.Count() > 1).Select(j => j.Key);
    return duplicateList.ToList();
}