在C#中，值类型是可变的还是不可变的? [英] In C# , Are Value types mutable or immutable ?

问题描述

值类型行为表明，我们持有的任何值都无法通过其他变量来更改.

但是我仍然对我在帖子标题中提到的内容感到困惑.有人可以澄清吗?

解决方案

值类型可以是可变的或(根据某些奇怪的边缘情况进行模数)是不可变的，具体取决于您如何编写它们. >

可变:

public struct MutableValueType
{
    public int MyInt { get; set; }
}

不可变:

public struct ImmutableValueType
{
    private readonly int myInt;
    public ImmutableValueType(int i) { this.myInt = i; }

    public int MyInt { get { return this.myInt; } }
}

内置值类型(int，double等) 是不可变的，但是您可以非常轻松地创建自己的可变struct.

一条建议:不要.可变值类型不是一个好主意，应该避免.例如，这段代码是做什么的:

SomeType t = new SomeType();
t.X = 5;

SomeType u = t;
t.X = 10;

Console.WriteLine(u.X);

这取决于.如果SomeType是值类型，它将显示5，这是一个非常令人困惑的结果.

请参阅此问题，以获取有关为什么应避免使用可变值类型的更多信息.

Value types behavior shows that whatever value we are holding cannot be changed through some other variable .

But I still have a confusion in my mind about what i mentioned in the title of this post . Can anyone clarify?

解决方案

Value types can be either mutable or (modulo some weird edge cases) immutable, depending on how you write them.

Mutable:

public struct MutableValueType
{
    public int MyInt { get; set; }
}

Immutable:

public struct ImmutableValueType
{
    private readonly int myInt;
    public ImmutableValueType(int i) { this.myInt = i; }

    public int MyInt { get { return this.myInt; } }
}

The built-in value types (int, double and the like) are immutable, but you can very easily create your own mutable structs.

One piece of advice: don't. Mutable value types are a bad idea, and should be avoided. For example, what does this code do:

SomeType t = new SomeType();
t.X = 5;

SomeType u = t;
t.X = 10;

Console.WriteLine(u.X);

It depends. If SomeType is a value type, it prints 5, which is a pretty confusing result.

See this question for more info on why you should avoid mutable value types.

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