问题描述

C# 中是否存在不允许您向其中添加重复项的集合?例如，用愚蠢的类

Is there a collection in C# that will not let you add duplicate items to it? For example, with the silly class of

public class Customer {
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Address { get; set; }

    public override int GetHashCode() {
        return (FirstName + LastName + Address).GetHashCode();
    }

    public override bool Equals(object obj) {
        Customer C = obj as Customer;
        return C != null && String.Equals(this.FirstName, C.FirstName) && String.Equals(this.LastName, C.LastName) && String.Equals(this.Address, C.Address);
    }
}

以下代码将(显然)抛出异常:

The following code will (obviously) throw an exception:

Customer Adam = new Customer { Address = "A", FirstName = "Adam", LastName = "" };
Customer AdamDup = new Customer { Address = "A", FirstName = "Adam", LastName = "" };

Dictionary<Customer, bool> CustomerHash = new Dictionary<Customer, bool>();
CustomerHash.Add(Adam, true);
CustomerHash.Add(AdamDup, true);

但是有没有一个类可以同样保证唯一性，但没有 KeyValuePairs?我认为 HashSet<T> 会这样做，但是在阅读了文档后，似乎该类只是一个集合实现(go figure).

But is there a class that will similarly guarantee uniqueness, but without KeyValuePairs? I thought HashSet<T> would do that, but having read the docs it seems that class is just a set implementation (go figure).

推荐答案

HashSet<T> 正是您要找的.来自 MSDN(已添加重点):

HashSet<T> is what you're looking for. From MSDN (emphasis added):

HashSet<T> 类提供高性能的集合操作.集合是不包含重复元素且其元素没有特定顺序的集合.

The HashSet<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.

请注意 HashSet.Add(T item) 方法 返回一个 bool -- true 如果项目被添加到集合中；false 如果项目已经存在.

Note that the HashSet<T>.Add(T item) method returns a bool -- true if the item was added to the collection; false if the item was already present.

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