为什么此代码段显示答案为6？ [英] Why does this snippet display the answer as 6?

问题描述

我的一个同学问了这个问题，我想确定我告诉他正确的答案。基本上下面的代码（确实显示6作为答案）困惑他，当它得到MessageBox.Show（（i - ）。ToString（））。

A classmate of mine asked this question, and I wanted to be sure that I was telling him the correct answer. Essentially the code below (which does indeed display "6" as the answer) confused him when it got to MessageBox.Show((i--).ToString());.

我的解释是递减操作（i--）实际上没有发生，因为它被传递给MessageBox对象的.Show方法。因此，它显示6，因为它实际上并没有将该值减少1.

My explanation was that the decrement operation (i--) isn't actually taking place, since it is being passed to the .Show method of the MessageBox object. So it displays 6 because it's not actually reducing that value by 1.

这是正确的解释吗？我从来没有试图抛出inc / dec操作，同时还显示值的同时，所以我不知道我的推理是否正确。谢谢！

Is this the correct explanation? I've never tried to throw inc/dec operations while also displaying values at the same time, so I'm not sure if my reasoning on this is correct. Thanks!

        int i = 6;            // I starts as 6...
        if (i >=4 )           // Then the check to see if i >= 4 is TRUE...
        {
            if( i == 5)       // The check to see if i == 5 is FALSE...
            {
                MessageBox.Show(i.ToString()); 
            }
            else
            {
                MessageBox.Show((i--).ToString());  // ****
            }
        }
        else 
        { 
            MessageBox.Show((i++).ToString());
        }

推荐答案

i - 返回i的值，并返回递减前的值。

i-- returns the value of i and returns the value before the decrement.

您应该按照词汇顺序）。

You should read it logically in the lexical order (as was intended by the creators) :

puts the value
and then decrements

如果是6之前，则返回6（打印），即使在i的值为5之后。

If it's 6 before, it returns 6 (which is printed) even if just after the value of i is 5.

请注意， - i 递减并返回递减的值。

Note that --i decrements and returns the decremented value.

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