=> 是什么?在 C# 中的属性签名中赋值 [英] What is the => assignment in C# in a property signature
问题描述
我遇到了一些代码,上面写着
public int MaxHealth =>内存[地址].IsValid ?Memory[地址].Read(Offs.Life.MaxHp):0;
现在我对 Lambda 表达式有点熟悉了.我只是没有看到它以这种方式使用它.
上面的语句和
有什么区别public int MaxHealth = x ?y:z;
您正在查看的是 表达式主体成员 不是 lambda 表达式.
当编译器遇到一个以表达式为主体的属性成员时,它本质上会将其转换为这样的getter:
public int MaxHealth{得到{返回内存[地址].IsValid?Memory[地址].Read(Offs.Life.MaxHp):0;}}
(您可以通过将代码注入一个名为 a> Expression-bodied 成员 - 就像大多数 C# 6 特性一样 - 只是 语法糖.这意味着它们不提供通过现有功能无法实现的功能.相反,这些新功能允许使用更具表现力和简洁的语法 如您所见,表达式主体成员有一些使属性成员更紧凑的快捷方式: 我将最后一点加粗,因为它与您的实际问题相关,我现在将回答. ...之间的区别 还有…… 是一样的区别... 还有…… 这 - 如果您了解属性 - 应该很明显. 不过要明确一点:第一个列表是一个在引擎盖下带有 getter 的属性,每次您访问它时都会调用它.第二个列表是一个带有字段初始值设定项的字段,当类型被实例化时,它的表达式只计算一次. 这种语法差异实际上非常微妙,可能会导致陷阱",Bill Wagner 在一篇题为 "AC# 6 问题:初始化与表达式实体成员". 虽然表达式主体成员是 lambda 表达式-like,但它们不是 lambda 表达式.根本区别在于 lambda 表达式会生成委托实例或表达式树.表达式主体成员只是编译器在幕后生成属性的指令.相似度(或多或少)以箭头( 我还要补充一点,表达式主体成员不限于属性成员.他们为所有这些成员工作: 添加在 C# 7.0 但是,它们不适用于这些成员: I came across some code that said Now I am somewhat familiar with Lambda expressions. I just have not seen it used it this way. What would be the difference between the above statement and
What you're looking at is an expression-bodied member not a lambda expression. When the compiler encounters an expression-bodied property member, it essentially converts it to a getter like this: (You can verify this for yourself by pumping the code into a tool called TryRoslyn.) Expression-bodied members - like most C# 6 features - are just syntactic sugar. This means that they don’t provide functionality that couldn't otherwise be achieved through existing features. Instead, these new features allow a more expressive and succinct syntax to be used As you can see, expression-bodied members have a handful of shortcuts that make property members more compact: I have made the final point bold because it is relevant to your actual question, which I will answer now. The difference between... And... Is the same as the difference between... And... Which - if you understand properties - should be obvious. Just to be clear, though: the first listing is a property with a getter under the hood that will be called each time you access it. The second listing is is a field with a field initializer, whose expression is only evaluated once, when the type is instantiated. This difference in syntax is actually quite subtle and can lead to a "gotcha" which is described by Bill Wagner in a post entitled "A C# 6 gotcha: Initialization vs. Expression Bodied Members". While expression-bodied members are lambda expression-like, they are not lambda expressions. The fundamental difference is that a lambda expression results in either a delegate instance or an expression tree. Expression-bodied members are just a directive to the compiler to generate a property behind the scenes. The similarity (more or less) starts and end with the arrow ( I'll also add that expression-bodied members are not limited to property members. They work on all these members: Added in C# 7.0 However, they do not work on these members: 这篇关于=> 是什么?在 C# 中的属性签名中赋值的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!return
语句,因为编译器可以推断出你想要返回表达式的结果get
关键字,因为它是由表达式主体成员语法的使用所暗示的.//表达式主体的成员属性public int MaxHealth =>X ?y:z;
//带有字段初始值设定项的字段公共 int MaxHealth = x ?y:z;
public int MaxHealth{得到{返回 x ?y:z;}}
public int MaxHealth = x ?y:z;
=>
)开始和结束.public int MaxHealth =>
Memory[Address].IsValid ?
Memory[Address].Read<int>(Offs.Life.MaxHp) :
0;
public int MaxHealth = x ? y:z;
public int MaxHealth
{
get
{
return Memory[Address].IsValid ? Memory[Address].Read<int>(Offs.Life.MaxHp) : 0;
}
}
return
statement because the compiler can infer that you want to return the result of the expressionget
keyword because it is implied by the use of the expression-bodied member syntax.// expression-bodied member property
public int MaxHealth => x ? y:z;
// field with field initializer
public int MaxHealth = x ? y:z;
public int MaxHealth
{
get
{
return x ? y:z;
}
}
public int MaxHealth = x ? y:z;
=>
).