Visual Studio 2017不显示错误，但存在构建错误。 [英] Visual studio 2017 doesn't show errors, but there are build errors.

问题描述

Visual Studio 2017没有在代码中显示任何错误，错误列表为空，但它表示在我尝试运行代码时存在构建错误。 （如果有帮助的话，它是一个控制台应用程序）



Visual Studio一直在为我试图制作的其他控制台应用程序执行此操作。



VS也显示其他错误，而不是导致构建错误的任何错误。



以下是代码：

Visual Studio 2017 isn't showing any errors in the code, and the error list is empty, but it says that there are build errors when I try to run my code. (it is a console application if that helps)

Visual Studio has been doing this for other console applications that i have been trying to make too.

VS is also showing other errors, just not whatever is causing the build errors.

Here is the code:

using System;
using System.Collections.Generic;

namespace ConsoleApp5
{
    class Program
    {
        static void Main()
        {
            int[] vals = {6, 5, 3, 1, 8, 7, 2, 4};
            //List<int> vals = new List<int> { 6, 5, 3, 1, 8, 7, 2, 4 };
            int n = 8;
            

            for (int i = 0; i < n; i++)//<= or <?
            {
                
                for (int j = 0; j < n - 1; j += 1 )
                {
                    if (vals[j] > vals[j + 1])
                    {
                        int x = vals[j];
                        int y = vals[j + 1];
                        vals[j] = y;
                        vals[j + 1] = x;
                        
                        //vals[j + 1] = vals[j];
                    }
                    
                }
            }

            foreach (int num in vals)
            {
                Console.WriteLine(vals[num]);
            }
            
            
            
            
        }
    }
}

我尝试了什么：



再次关闭VS，

再次打开和关闭电脑，

再次关闭我的电脑，

制作一个全新的控制台应用程序，



这些都没有改变任何东西。

What I have tried:

turning VS off and on again,
turning my computer on and off again,
powering my computer off and on again,
making a completely new console app,

none of these changed anything.

推荐答案

编译并不意味着你的代码是正确的！ ：笑：

将开发过程想象成编写电子邮件：成功编译意味着您使用正确的语言编写电子邮件 - 例如英语而不是德语 - 而不是电子邮件包含您的邮件想发送。



编译时并不是所有的错误信息都会发生 - 有些是在你运行你的代码时发生的，而且它确实是愚蠢的。



所以现在你进入第二阶段的开发（实际上它是第四或第五阶段，但你会在之后的阶段进入）：测试和调试。



首先看看它做了什么，以及它与你想要的有何不同。这很重要，因为它可以为您提供有关其原因的信息。例如，如果程序旨在让用户输入一个数字并将其翻倍并打印答案，那么如果输入/输出是这样的：

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

Not all error messages happen when you compile - some happen when you run your code, and it does something silly.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

然后很明显问题出在将它加倍的位 - 它不会将自身加到自身上，或者将它乘以2，它会将它自身相乘并返回输入的平方。

所以，你可以查看代码和很明显，它在某处：

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

private int Double(int value)
   {
   return value * value;
   }

一旦你知道可能出现的问题，就开始使用调试器找出原因。在方法的第一行放置一个断点，然后运行你的应用程序。当它到达断点时，调试器将停止，并将控制权移交给您。您现在可以逐行运行代码（称为单步执行）并根据需要查看（甚至更改）变量内容（哎呀，您甚至可以更改代码并在需要时再试一次）。 />
在执行代码之前，请考虑代码中的每一行应该做什么，并将其与使用Step over按钮依次执行每一行时实际执行的操作进行比较。它符合您的期望吗？如果是这样，请转到下一行。

如果没有，为什么不呢？它有什么不同？

希望这可以帮助你找到代码的哪个部分有问题，以及问题是什么。

这是一项技能，它是一个值得开发的，因为它可以帮助你在现实世界和发展中。和所有技能一样，它只能通过使用来改善！



我甚至会给你一个线索： foreach是什么吗？它围绕循环在 num 中放入什么值？如果您不确定，请使用调试器进行检查，yoru问题应该变得明显。

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

I'll even give you a clue: what does foreach do? What value doe it put in num as it goes round the loop? If you aren't sure, use the debugger to check and yoru problem should become obvious.

这是问题的最后一个循环。您正在使用数组中的实际值作为数组的索引：

It is your final loop that is the problem. You are using the actual value in the array as an index into the array:

foreach (int num in vals)
{
    Console.WriteLine(vals[num]);
}

它应该是：

It should be:

foreach (int num in vals)
{
    Console.WriteLine(num); // num is already the actual array item.
}

[edit]

顺便提一句，你需要了解编译，链接和执行错误之间的区别。你在这里遇到的是执行错误。

[/ edit]

[edit]
Incidentally you need to learn the difference between compile, link and execution errors. What you had here was an execution error.
[/edit]

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