C＃：使用错误，如果/开关：＆QUOT;局部变量已经在这个范围与定义QUOT; [英] C# : error using if/switch : "Local variable already defined in this scope"

问题描述

我是新的C＃和我的问题可能是简单的，但我不明白这一点：

I'm new to C# and my problem is probably simple, but I don't get it:

我需要一些值分配给根据条件的阵列。
所以，我可以使用开关语句的如果检查的条件。

I need to assign some values to an array depending on a condition. So I can use "if" of "switch" statement for checking the condition.

不过，如果我用切换然后我得到一个错误在此范围内已定义的局部变量。

However,if I use "switch" then I get an error "Local variable already defined in this scope".

如果我用如果，那么我得到一个错误并不在目前的情况下存在

And if I use "if" then I get an error "does not exist in current context"

例如：

int x;
x=1;

//1:
//a)  does work...
if (x==1)
{
        string[,] arraySpielfeld2d = 
        {
         {"1", "1" },
         {"1", "1" }
        };
}
else
{
        string[,] arraySpielfeld2d = 
        {
         {"1", "1" },
         {"1", "1" }
        };
}


//b) but this does not work
MessageBox.Show(arraySpielfeld2d[0,0]);  //error: does not exist in current context


//2) doesn't work at all
switch (x)
    {

    case 1:
        string[,] arraySpielfeld2d = 
        {
         {"1", "1" },
         {"1", "1" }
        };
        break;


    case 2:
        string[,] arraySpielfeld2d =    //error:Local variable already defined in this scope
        {
         {"2", "2" },
         {"2", "2" }
        };
        break;

    }

因此​​，使用如果我至少可以填充阵列（1A）...但我不能访问数组元素（1B）...
使用开关不工作的。

So using "if" I can at least populate the array (1a)...but I can not access the array elements (1b)... Using "switch" doesn't work at all.

所以，我怎么能和分配可以根据条件，然后到一个数组访问值（如果/开关）？

So how could I assign and then access values to an array depending on a condition (if/switch)?

我使用Visual Studio 2010。

I use Visual Studio 2010.

感谢

推荐答案

您已经宣布的范围阵列的如果，但你想从外部访问。这是行不通的。你必须在外面声明。但你不能使用集合初始化语法：

You have declared the array in the scope of the if, but you want to access it from outside. That doesn't work. You have to declare it outside. But then you can't use the collection initializer syntax:

int x;
x=1;
string[,] arraySpielfeld2d = new string[2,2];

if (x == 1)
{
        arraySpielfeld2d[0,0] = "1";
        arraySpielfeld2d[0,1] = "1";
        arraySpielfeld2d[1,0] = "1";
        arraySpielfeld2d[1,1] = "1";
}
else if(x == 2)
{
    arraySpielfeld2d[0, 0] = "2";
    arraySpielfeld2d[0, 1] = "2";
    arraySpielfeld2d[1, 0] = "2";
    arraySpielfeld2d[1, 1] = "2";
}
MessageBox.Show(arraySpielfeld2d[0,0]);

同样是一个开关如果你使用括号（ {} ），这也创造了一个新的作用域真

The same is true for a switch which also creates a new scope if you use braces({ }).

请注意，您不需要在这种情况下，如果或开关，似乎你总是希望使用 X ：

Note that you don't need an if or switch in this case, it seems that you always want to use x:

string val = x.ToString();
string[,] arraySpielfeld2d = 
{
     {val, val },
     {val, val }
};

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