我读了这个问题 (<< a href='"https://stackoverflow.com/ questions/10494074/ what - is -the -scope-f-a-lambda-可变-in-c-'?
但它是关于兰巴达变异范围 在LINQ查询。
现在回答我的问题<强/强>
假设我有一个很简单的LINQ查询
var Foo = FoobBar.Select(x => x);
var x = somefunction();
编译者说: A 本地变量 x 不能在此范围内声明, 因为它会赋予 x 不同的含义, 而 x 已经在子范围中用于表示其他 。
为什么如此? 当 LINQ 查询结束时, Lambda 变量应该停止存在吗?
EDIT: 在读完答复后,我得出结论认为,其外部 x (从功能返回),其范围在LINQ 查询范围内。
它与LINQ无关,它与儿童范围有关。
例如:
foreach (var bar in FooBar.Bars)
{
var x = FooBar.GetFoo();
}
var x = new Foo();
从编译器中产生完全相同的错误消息 。
To fix that you just have to place variables in different (non-nesting) scopes. 例如:
foreach (var bar in FooBar.Bars)
{
var x = FooBar.GetBar();
}
{
var x = new Foo();
}
让我们仔细看一看,
var Foo = FoobBar.Select(x => x);
表达式中 x 结尾的 x 真实范围
var x = somefunction()
现在,这很有趣, 这是用于同样使用 amda 表达式的整个方法的范围, 所以汇编者无法区分, 因为后者的范围与前者重叠。 并且非常信息化的信息太“ 强” 给 x 带来不同的含义, 已经在子范围 (在您的情况下选择) (在您的情况下选择)
想想C#如果允许这两个变量在同一范围水平上存在,这是不可能做到的: 您如何对 C # 说您想要指派名为 x 的 Action 代表为 Kyrie 变量; 或者反之亦然, 您如何对 C # 说您想要使用整数投影本身? C # 将如何解决这个问题? C#范围界定决议非常一致,无论你在其他变量之前还是在其他变量之后宣布,它们都是相同的。例如,http://www.anicehumble.com/2012/05/java-said-c-said-scrames-conference.html。 C# 不容许您编译一个程序, 其变量名称在相同的级别上存在 。 这一切都是为了用“强势”的不含糊的方式 < 强势 " /强势 " 向汇编者表达你的“强势 " /强势 " 。 C#在这方面做了很好的工作。 它并不清楚(对编译者来说) 您指的是第二个 x (在 如果你写了这个: 使羊羔中的 无法在相同范围内声明同名的两个变量。 “同一范围”意指两者均在目前的范围之内。 一个在当期,另一个在儿童范围。 这是设计好的, 用于从 < code> int 到 ambda 引用的任何变量 。
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var Foo = FoobBar.Select(y => x);
var x = somefunction();
x 与某些功能结果相冲突。
void method()
{
int a;
int a; //wrong!
}
void method()
{
int a;
for(;;)
{
int a; //wrong again!
}
}
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