C# 即使已声明，名称也不存在

我的代码

static int IntCheck(string num)
{
    int value;
    if (!int.TryParse(num, out value))
    {
        Console.WriteLine("I am sorry, I thought I said integer, let me check...");
        Console.WriteLine("Checking...");
        System.Threading.Thread.Sleep(3000);
        Console.WriteLine("Yup, I did, please try that again, this time with an integer");
        int NewValue = IntCheck(Console.ReadLine());
    }
    else
    {
        int NewValue = value;
    }
    return NewValue;
 }

错误

当前上下文中不存在名称“NewValue”（第33行）

---

你需要在外面申报

static int IntCheck(string num)
{
    int value;
    int NewValue;
    if (!int.TryParse(num, out value))
    {
        Console.WriteLine("I am sorry, I thought I said integer, let me check...");
        Console.WriteLine("Checking...");
        System.Threading.Thread.Sleep(3000);
        Console.WriteLine("Yup, I did, please try that again, this time with an integer");
        NewValue = IntCheck(Console.ReadLine());
    }
    else
    {
        NewValue = value;
    }
    return NewValue;
 }

---

NewValue在

if

和

else

块内的范围内。您需要将声明移到块之外

static int IntCheck(string num)
{
    int value;
    int NewValue;
    if (!int.TryParse(num, out value))
    {
        Console.WriteLine("I am sorry, I thought I said integer, let me check...");
        Console.WriteLine("Checking...");
        System.Threading.Thread.Sleep(3000);
        Console.WriteLine("Yup, I did, please try that again, this time with an integer");
        NewValue = IntCheck(Console.ReadLine());
    }
    else
    {
        NewValue = value;
    }
    return NewValue;
 }

---

定义方法顶部的

NewValue

。由于

NewValue

的两个定义都位于

if

和

else

块的内部，因此无法从外部访问它们。旁注：在询问编译器错误之前，最好先检查MSDN对此的说明，即在这种情况下：如果在循环或

try

或

if

块中声明变量，然后试图从封闭的代码块或单独的代码块访问它，则经常发生此错误