c# 学习笔记 - 集合(Dictionary)

1.概论

1.1 Dictionary 特性

• 1. 键值对容器，底层使用哈希表实现.
• 2. 键唯一，不可以重复添加.

 

1.2 .NET API

  API介绍
Dictionary 类
 

2. 基本使用

2.1 样例

static void Main() {
    Dictionary<int, string> dic = new Dictionary<int, string>();

    dic.Add(1, "AA"); // 新增
    dic.Add(2, "BB");
    foreach(var item in dic) Console.WriteLine(item.Key + " " + item.Value);
    Console.WriteLine("=======================================");

    dic[1] = "CC"; // 修改 dic[key] = value; 
    foreach(var item in dic) Console.WriteLine(item.Key + " " + item.Value);
    Console.WriteLine("=======================================");


    dic.Remove(1); // 删除
    foreach(var item in dic) Console.WriteLine(item.Key + " " + item.Value);
    Console.WriteLine("=======================================");
}
/*
1 AA
2 BB
=======================================
1 CC
2 BB
=======================================
2 BB
=======================================
*/

 

3. 添加类操作

3.1 Add、TryAdd

• Add – 添加指定键值对
• TryAdd – 尝试添加指定键值对

static void Main() {
    Dictionary<int, string> dic = new Dictionary<int, string>();

    dic.Add(1, "AA");
    dic.Add(2, "BB");
    Console.WriteLine(dic.TryAdd(2, "B2"));
    Console.WriteLine(dic.TryAdd(3, "CC"));
    foreach(var item in dic) {
        Console.WriteLine(item.Key + " " + item.Value);
    }
}

/*
False
True
1 AA
2 BB
3 CC
*/

 

4. 修改类操作

4.1 Remove、Clear

• Remove – 清除指定键值对
• Clear-- 删除所有键值对

static void Main() {
    Dictionary<int, string> dic = new Dictionary<int, string>();

    dic.Add(1, "AA");
    dic.Add(2, "BB");
    dic.Add(3, "CC");
    dic.Remove(2); // Remove(key)
    foreach(KeyValuePair<int, string> item in dic) {
        Console.WriteLine(item.Key + " " + item.Value);
    }

    dic.Clear();
    foreach(KeyValuePair<int, string> item in dic) {
        Console.WriteLine(item.Key + " " + item.Value);
    }
}

/*
1 AA
3 CC
*/