尝试HashSet:

The HashSet(Of T) class provides high-performance set operations. A set is a collection that contains no duplicate elements, and whose elements are in no particular order... The capacity of a HashSet(Of T) object is the number of elements that the object can hold. A HashSet(Of T) object's capacity automatically increases as elements are added to the object. The HashSet(Of T) class is based on the model of mathematical sets and provides high-performance set operations similar to accessing the keys of the Dictionary(Of TKey, TValue) or Hashtable collections. In simple terms, the HashSet(Of T) class can be thought of as a Dictionary(Of TKey, TValue) collection without values. A HashSet(Of T) collection is not sorted and cannot contain duplicate elements...

尝试HashSet:

The HashSet(Of T) class provides high-performance set operations. A set is a collection that contains no duplicate elements, and whose elements are in no particular order... The capacity of a HashSet(Of T) object is the number of elements that the object can hold. A HashSet(Of T) object's capacity automatically increases as elements are added to the object. The HashSet(Of T) class is based on the model of mathematical sets and provides high-performance set operations similar to accessing the keys of the Dictionary(Of TKey, TValue) or Hashtable collections. In simple terms, the HashSet(Of T) class can be thought of as a Dictionary(Of TKey, TValue) collection without values. A HashSet(Of T) collection is not sorted and cannot contain duplicate elements...

如果你使用。net 4.0或更高版本:

在需要排序的情况下，使用SortedSet<T>。否则，如果没有，则使用HashSet<T>，因为它是O(1)用于搜索和操作操作。而SortedSet<T>对于搜索和操作操作是O(log n)。

在CodePlex上看看PowerCollections。除了Set和OrderedSet，它还有一些其他有用的集合类型，如Deque, MultiDictionary, Bag, OrderedBag, OrderedDictionary和OrderedMultiDictionary。

对于更多的集合，还有C5通用集合库。

我知道这是一个旧线程，但我遇到了同样的问题，发现HashSet非常不可靠，因为给定相同的种子，GetHashCode()返回不同的代码。我想，为什么不用List隐藏add方法呢

public class UniqueList<T> : List<T>
{
    public new void Add(T obj)
    {
        if(!Contains(obj))
        {
            base.Add(obj);
        }
    }
}

因为List仅使用Equals方法来确定相等性，所以可以在T类型上定义Equals方法，以确保获得所需的结果。

我使用Dictionary<T对象>的包装器，在值中存储空值。这就提供了O(1)键的添加、查找和删除，并且在所有意图和目的上都像一个集合。