为什么我不能在C＃的不同范围内声明一个具有相同名称的变量？

Why can't I declare a variable with the same name in different scopes in C#?

本问题已经有最佳答案，请猛点这里访问。

不确定这是否是因为C编译器特别挑剔，但我尝试在C中这样做：

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public static void Main()
{
bool result = true; // some dummy value
if(result)
{
int x = 5;
Console.WriteLine(x);
}

int x = 10;
Console.WriteLine(x);
}

编译器抱怨变量名"x"已经被使用：

A local variable named 'x' cannot be declared in this scope because it
would give a different meaning to 'x', which is already used in a
'child' scope to denote something else.

我知道它认为这是一个范围问题，但为什么会这么想呢？

如果我在爪哇复制相同的代码，就没有问题了。

正如@blackfrog正确指出的那样，每个{ }都没有启动新的作用域。根据C语言规范第3.3节：

? Each method declaration, indexer declaration, operator declaration, instance constructor declaration and anonymous function creates a new declaration space called a local variable declaration space. Names are introduced into this declaration space through formal parameters (fixed-parameters and parameter-arrays) and type-parameters. The body of the function member or anonymous function, if any, is considered to be nested within the local variable declaration space. It is an error for a local variable declaration space and a nested local variable declaration space to contain elements with the same name.

(强调矿山)

来自msdn编译器错误cs0136

For each occurrence of a given identifier as a simple-name in an
expression or declarator, within the local variable declaration space
(§3.3) immediately enclosing that occurrence, every other occurrence
of the same identifier as a simple-name in an expression or declarator
must refer to the same entity. This rule ensures that the meaning of a
name is always the same within a given block, switch block, for-,
foreach- or using-statement, or anonymous function.

作为第二个参考，检查C答案中的变量范围混淆，您可以在中找到好的信息。

You are allowed to use the same variable name in non-overlapping
scopes. If one scope overlaps another, though, you cannot have the
same variable declared in both. The reason for that is to prevent you
from accidentally using an already-used variable name in an inner
scope

并非所有的{}都开始了新的作用域。if块中声明的整数仍与函数位于同一堆栈上。