不同的吸气剂样式之间的C#差异 [英] Difference in C# between different getter styles

问题描述

有时我会在getter的属性中看到缩写.例如.这两种类型:

I do sometimes see abbreviations in properties for the getter. E.g. those two types:

public int Number { get; } = 0

public int Number => 0;

有人可以告诉我两者之间是否有任何区别.他们的行为如何?它们都是只读的吗?

Can someone please tell me if there are any differences between those two. How do they behave? Are both of them read-only?

推荐答案

是的，它们都是只读的，但是有所不同.在第一个中，有一个后备字段，该后备字段在执行构造函数之前被初始化为0.您可以仅在构造函数中更改值 ，就像常规的只读字段一样. getter本身仅返回该字段的值.

Yes, both of them are read-only, but there is a difference. In the first one, there's a backing field which is initialized to 0 before the constructor is executed. You can change the value only in the constructor, just like a regular read-only field. The getter itself just returns the value of the field.

在第二个中，getter每次都返回0，不涉及任何字段.

In the second one, the getter just returns 0 every time, with no field involved.

因此，要完全避免使用任何自动实现的属性或表达式强成员，我们可以:

So to avoid using any automatically implemented properties or expression-bodied members at all, we have:

第一版

private readonly int _number = 0;
public int Number { get { return _number; } }

第二版

public int Number { get { return 0; } }

下面是一个更清晰的区别示例:

A clearer example of the difference might be seen like this:

public DateTime CreationTime { get; } = DateTime.UtcNow;
public DateTime CurrentTime => DateTime.UtcNow;

如果创建单个对象，则其CreationTime属性将始终给出相同的结果-因为它存储在只读字段中，并在对象构造时初始化.但是，每次访问CurrentTime属性时，都会导致对DateTime.UtcNow进行求值，因此可能会得到不同的结果.

If you create a single object, its CreationTime property will always give the same result - because it's stored in a readonly field, initialized on object construction. However, every time you access the CurrentTime property, that will cause DateTime.UtcNow to be evaluated, so you'll get a potentially different result.

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