Question

我很难用我编写的以下方法来识别问题。由于错误“并非所有代码路径都返回值”，它当前不会编译：

private static int compareVersionNumbers(string installedVersion, string requiredVersion)
    {
        if (installedVersion.Equals(requiredVersion))
        {
            Console.WriteLine("Versions are identical.");
            return 0;
        }
        else if (installedVersion != (requiredVersion))
        {
            // Split version strings into arrays.
            List<string> versionArray = installedVersion.Split('.').ToList<string>();
            List<string> otherVersionArray = requiredVersion.Split('.').ToList<string>();

            int count = 0;

            while ((count < versionArray.Count()) && (count < otherVersionArray.Count()))
            {

                // Fetch current version component
                int currentPart = Convert.ToInt32(versionArray.ElementAt(count));
                int otherPart = Convert.ToInt32(otherVersionArray.ElementAt(count));

                if (currentPart > otherPart)
                {
                    Console.WriteLine(installedVersion + " is greater than " + requiredVersion);
                    return 1;
                    break;
                }
                else if (currentPart < otherPart)
                {
                    Console.WriteLine(installedVersion + " is less than " + requiredVersion);
                    return -1;
                    break;
                }
                count++;

            }

        }
    }

一般来说，VisualStudio的调试器中是否有任何有用的工具可用于排除无法访问的代码？

Answer 1

您有一个if和一个else if声明。但是你没有else语句，这意味着如果你的所有条件都是假的，那么你的函数就不会返回值。如果恰好相反，你的elseif语句改为else语句您的if语句（看起来像这样），或返回函数的值结束。

Answer 2

您遇到的问题意味着编译器至少找到了一种函数不会返回值的方法。这些特殊情况如下：

while循环后没有返回值。可能是while甚至无法运行。
else if阻止后else return -1;

Answer 3

你的函数只在if子句中有2个if子句和return指令。对于第二个if子句，你应该有1个else子句。

Answer 4

我认为问题是编译器在块中分析你的代码它找到一个块（内部的if），它不返回所需的整数

此外，如果while的所有内部路径都返回了编译器仍然抱怨的内容，因为else if块不会返回任何内容

让我根据您的代码展示一个人为的例子，其中包含一些修正建议：

int Test()
{
    int a = 10;
    if(a < 10)
    {
        // Always false but the compiler is happy here 
        // because this block returns the integer
        return 1;
    }
    else if(a==10)
    {
        // We always enter here but the compiler doesn't check at this point 
        // if the condition is true or not neither what happen inside the while block
        // It looks at the else if and conclude that you don't return the integer 

        while(a < 20)
        {
            // Again, we know that we always enter the while block but 
            // the analysis is not executing our code and  
            // it is already been decided that something is wrong
            if(a < 15)
                return 2;
            else if(a < 18)
                return 3;
            else
                return 4;  // Adding this else doens't make any difference
            a++;
        }

        ??????? here the compiler wants something to return
    }
    else
    {
        // happy here because the block returns the integer
        // but, again,  adding this else doesn't make any difference
        return 5;
    }
}

仍然错误没有消失，对于编译器，内部if else不返回整数，而我们的逻辑告诉我们这是不可能的

Answer 5

原来我只需要在if / if else if块后再返回一次：</ p>

private static int compareVersionNumbers(string installedVersion, string requiredVersion)
    {
        if (installedVersion.Equals(requiredVersion))
        {
            Console.WriteLine("Versions are identical.");
            return 0;
        }
        else if (installedVersion != (requiredVersion))
        {
            // Split version strings into arrays.
            List<string> versionArray = installedVersion.Split('.').ToList<string>();
            List<string> otherVersionArray = requiredVersion.Split('.').ToList<string>();

            int count = 0;

            while ((count < versionArray.Count()) && (count < otherVersionArray.Count()))
            {

                // Fetch current version component
                int currentPart = Convert.ToInt32(versionArray.ElementAt(count));
                int otherPart = Convert.ToInt32(otherVersionArray.ElementAt(count));

                if (currentPart > otherPart)
                {
                    Console.WriteLine(installedVersion + " is greater than " + requiredVersion);
                    return 1;
                    break;
                }
                else if (currentPart < otherPart)
                {
                    Console.WriteLine(installedVersion + " is less than " + requiredVersion);
                    return -1;
                    break;
                }
                count++;

            }

        }
        return 0;
    }

无法访问的代码＃2

5 个答案: