迭代器变量超出C#的范围

发布时间：2020-12-16 01:54:39 所属栏目：百科来源：网络整理

导读：为什么我用C#写这个： for(int myVar = 0; myVar10; myVar++){//do something here}//then,if I try:int myVar = 8;//I get some error that the variable is already declared.//but if I try:Console.WriteLine(myVar);//then I get the error that the va

为什么我用C#写这个：

for(int myVar = 0; myVar<10; myVar++)
{
//do something here
}

//then,if I try:
int myVar = 8;
//I get some error that the variable is already declared.

//but if I try:
Console.WriteLine(myVar);
//then I get the error that the variable is not declared.

我最常说的有点混乱.有谁知道为什么C#编译器会这样做？

解决方法

该规则以及其他几个相关规则将在 this blog post of Eric Lippert’s中讨论.

这里违反的特定规则是：

2) It is illegal to have two local variables of the same name in the same local variable declaration space or nested local variable declaration spaces.

特别值得注意的是,关于规则存在的原因如下：

the purpose of all of these rules is to prevent the class of bugs in which the reader/maintainer of the code is tricked into believing they are referring to one entity with a simple name,but are in fact accidentally referring to another entity entirely. These rules are in particular designed to prevent nasty surprises when performing what ought to be safe refactorings.

通过允许你所描述的内容,它可以产生看似良性的重构,例如将for循环移动到另一个声明之后,导致极其不同的行为.

（编辑：李大同）

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