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theme: smartblue

一、 Record

1.1 基础用法

``` internal record Student { public int Id { get; set; } = 24;

public string Name { get; set; } = "xyy";

} ```

``` Person person = new Person("F","L"); Console.WriteLine($"fitst name {person.firstName}, last name {person.lastName}");

// 将 对象属性 赋予到 变量 person.Deconstruct(out string firstName, out string lastName); Console.WriteLine($"fitst name {firstName}, last name {lastName}"); ```

1.2 不可变性

默认 Record 属性不可变，Person 相当于 Person2 写法，只能在初始化值时设置内容

``` internal record Person(String firstName,string lastName);

internal record Person2() { public string fitstName { get; init; } = default!; public string lastName { get; init; } = default!; }; ``` 也可添加 set 允许,属性能够改变

internal record Person3() { public string fitstName { get; set; } = default!; public string lastName { get; set; } = default!; };

1.3 值相等性

若要依次比较两个 Record 对象是否相等，可直接使用=

``` Person person1 = new Person("F","L"); Person person2 = new Person("F", "L"); Console.WriteLine(person2 == person1); // true

Person person3 = new Person("L", "F"); Console.WriteLine(person3 == person2); // false ```

若要比较引用地址是否相等，可使用 ReferenceEquals 方法 Person person1 = new Person("F","L"); Person person2 = new Person("F", "L"); Console.WriteLine(ReferenceEquals(person1,person2)); // false

1.4 非破坏性变换

可以使用 with 关键词修改指定属性

Person person3 = person2 with { firstName="T"}; Console.WriteLine(person2); Console.WriteLine(person3); 执行结果如下：

Person { firstName = F, lastName = L } Person { firstName = T, lastName = L }

二、 仅限 Init 的资源库

添加 init 后，仅限于初始化时可以赋值

internal class Person2() { public string fitstName { get; init; } = default!; public string lastName { get; init; } = default!; };

三、 目标类型的 new 表达式

// 原写法 Student student1 = new Student(); // 修改后 Student student2 = new();

并且传入方法的参数为对象时，也可简写 ``` MyFunc(new());

void MyFunc(Student student){

}; ```