Question

代码告诉我输入何时不是数字，但是如果代码同时也写入else 我相信这与我在顶部双变量中将数字0分配给doubleNr有关，但如果我没有，我得到 使用未分配的局部变量'doubleNr' 另外，我在哪里写下 doubleNr = myMethod（intNr）; 行？
在try块中还是在catch和if块之间？

int intNr; double doubleNr = 0; while (doubleNr < 20 || doubleNr > 30) { Console.WriteLine("Enter your number: "); string strNr = Console.ReadLine(); try { intNr = Convert.ToInt32(strNr); doubleNr = myMethod(intNr); // Should this line go here? } catch { Console.WriteLine("Number must be INT"); } // or should it go here? if (doubleNr < 20) { Console.WriteLine("Try a higher number."); } else if (doubleNr > 30) { Console.WriteLine("Try a lower number."); } } Console.WriteLine("That is a good number.");

Answer 1

这可能不值得回答，但我只是想在你的代码中指出一些事情。由于您需要使用try-catch，因此您可以简单地实现retry-catch。要做到这一点，你应该使用while(true)和try-catch逻辑来控制程序的流程，如@Pikoh所说。

public static void Main(string[] args)
{
    int intNr;
    double doubleNr = 0;
    while(true)
    {
        try
        {
            Console.WriteLine("Enter your number: ");
            string strNr = Console.ReadLine();
            doubleNr = Int32.Parse(strNr);
            if(doubleNr < 20)
            {
                throw new Exception("Try a higher number.");
            }
            else if(doubleNr > 30)
            {
                throw new Exception("Try a lower number.");
            }
            else
            {
                Console.WriteLine("That is a good number.");
                break;
            }
        }
        catch(FormatException e)
        {
            Console.WriteLine("Enter a valid number.");
            continue;
        }
        catch(Exception ex)
        {
            Console.WriteLine(ex.Message);
            continue;
        }
    }
}

在这里，您可以看到while循环不会调节您的程序，try-catch逻辑将控制它。当然还有其他方法可以做到这一点，但这只是对代码的重组。

正如您所知，还有更好的方法可以做到这一点。您可以使用Int32.TryParse()，在这种情况下最好。无需使用任何try-catch块。

public static void Main(string[] args)
{
    int intNr;
    double doubleNr = 0;
    while(true)
    {
        Console.WriteLine("Enter your number: ");
        string strNr = Console.ReadLine();
        int value;
        if(Int32.TryParse(strNr, out value))
        {
            doubleNr = value;
        }
        else
        {
            Console.WriteLine("Enter a valid number: ");
            continue;
        }
        if(doubleNr < 20)
        {
            Console.WriteLine("Try a higher number.");
            continue;
        }
        else if(doubleNr > 30)
        {
            Console.WriteLine("Try a lower number.");
            continue;
        }
        else 
        {
            Console.WriteLine("That is a good number."); 
            break;
        }
    }
}

Answer 2

如果要在异常或任何其他条件下跳过当前循环步骤，请使用continue语句。

continue语句将控制传递给下一次迭代附上，发表，发表或发表声明的声明。

这是带有continue语句的代码示例。

int intNr;
double doubleNr = 0;

while (doubleNr < 20 || doubleNr > 30)
{
    Console.WriteLine("Enter your number: ");
    string strNr = Console.ReadLine();
    try
    {
        intNr = Convert.ToInt32(strNr);
        // if you want to catch any exceptions in this method then leave it there 
        // otherwise you can move it outside try/catch block            
        doubleNr = myMethod(intNr);  

    }
    catch
    {
        Console.WriteLine("Number must be INT");
        continue; // return to the beginning of your loop
    }

    if (doubleNr < 20)
    {
        Console.WriteLine("Try a higher number.");
        continue; // return to the beginning of your loop
    }
    // do not need else since code wont reach this line if doubleNr is < 20
    if (doubleNr > 30) 
    {
        Console.WriteLine("Try a lower number.");                        
        continue; // return to the beginning of your loop
    }
}
Console.WriteLine("That is a good number.");

循环，尝试捕捉

2 个答案: