4-3-2.C# 数据容器 - Dictionary 扩展（Dictionary 存储对象的特性、Dictionary 与数组的转换）

Dictionary 概述

1. Dictionary<TKey, TValue> 存储的是键值对（Key - Value），通过键（Key）来存储或修改值（Value）

2. Dictionary<TKey, TValue> 存储的键值对是无序的

3. Dictionary<TKey, TValue> 存储的键是不可重复的

4. Dictionary<TKey, TValue> 支持泛型，可以指定存储的键值对的类型

5. Dictionary<TKey, TValue> 不是线程安全的，在多线程环境中需要谨慎使用

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一、Dictionary 存储对象的特性

1. Dictionary 存储对象或对对象进行检测时（对象作为键或值时），对于没有重写 Equals 和 GetHashCode 方法的对象可能不太方便

internal class Person
{public String name;public int age;public Person() { }public Person(string name, int age){this.name = name;this.age = age;}
}

Dictionary<Person, string> messageDict = new Dictionary<Person, string>();messageDict.Add(new Person("Alice", 30), "Hello World 1");
messageDict.Add(new Person("Bob", 25), "Hello World 2");Console.WriteLine(messageDict.ContainsKey(new Person("Alice", 30)));
Console.WriteLine(messageDict.ContainsKey(new Person("Alice", 31)));

# 输出结果False
False

Dictionary<string, Person> personDict = new Dictionary<string, Person>();personDict.Add("Alice", new Person("Alice", 30));
personDict.Add("Bob", new Person("Bob", 25));Console.WriteLine(personDict.ContainsValue(new Person("Alice", 30)));
Console.WriteLine(personDict.ContainsValue(new Person("Alice", 31)));

# 输出结果False
False

2. Dictionary 存储对象或对对象进行检测时（对象作为键或值时），对于重写 Equals 和 GetHashCode 方法的对象比较方便

internal class Staff
{public String name;public int age;public Staff() { }public Staff(string name, int age){this.name = name;this.age = age;}// 重写 Equals 方法public override bool Equals(object obj){// 检查是否为同一个对象的引用if (obj == this) return true;// 检查对象是否为空if (obj == null) return false;// 检查类型是否相同if (obj.GetType() != this.GetType()) return false;// 将 obj 转换为 Staff 类型并进行属性比较Staff staff = obj as Staff;bool agesAreEqual = age == staff.age;bool namesAreEqual = name == null ? null == staff.name : name.Equals(staff.name);return agesAreEqual && namesAreEqual;}public override int GetHashCode(){// 使用属性生成哈希码int hash = 17;hash = hash * 23 + name?.GetHashCode() ?? 0;hash = hash * 23 + age.GetHashCode();return hash;}
}

Dictionary<Staff, string> messageDict = new Dictionary<Staff, string>();messageDict.Add(new Staff("Alice", 30), "Hello World 1");
messageDict.Add(new Staff("Bob", 25), "Hello World 2");Console.WriteLine(messageDict.ContainsKey(new Staff("Alice", 30)));
Console.WriteLine(messageDict.ContainsKey(new Staff("Alice", 31)));

# 输出结果True
False

Dictionary<string, Staff> staffDict = new Dictionary<string, Staff>();staffDict.Add("Alice", new Staff("Alice", 30));
staffDict.Add("Bob", new Staff("Bob", 25));Console.WriteLine(staffDict.ContainsValue(new Staff("Alice", 30)));
Console.WriteLine(staffDict.ContainsValue(new Staff("Alice", 31)));

# 输出结果True
False

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二、Dictionary 与数组的转换

1、Dictionary 转数组

1. Dictionary 转键值对数组

Dictionary<string, int> dict = new Dictionary<string, int>();dict.Add("Alice", 30);
dict.Add("Bob", 25);KeyValuePair<string, int>[] array = dict.ToArray();foreach (KeyValuePair<string, int> kvp in array)
{Console.WriteLine($"{kvp.Key} - {kvp.Value}");
}

# 输出结果Alice - 30
Bob - 25

2. Dictionary 转键数组

Dictionary<string, int> dict = new Dictionary<string, int>();dict.Add("Alice", 30);
dict.Add("Bob", 25);KeyValuePair<string, int>[] array = dict.ToArray();foreach (KeyValuePair<string, int> kvp in array)
{Console.WriteLine($"{kvp.Key} - {kvp.Value}");
}

# 输出结果Alice
Bob

3. Dictionary 转值数组

Dictionary<string, int> dict = new Dictionary<string, int>();dict.Add("Alice", 30);
dict.Add("Bob", 25);string[] array = dict.Keys.ToArray();foreach (string item in array)
{Console.WriteLine(item);
}

# 输出结果30
25

2、数组转 Dictionary

var array = new (string, int)[]
{("Alice", 30),("Bob", 25)
};Dictionary<string, int> dict = array.ToDictionary(kvp => kvp.Item1, kvp => kvp.Item2);foreach (KeyValuePair<string, int> kvp in dict)
{Console.WriteLine($"{kvp.Key} - {kvp.Value}");
}

# 输出结果Alice - 30
Bob - 25