Question

I’ve found this example which returns custom type Car objects in reverse order.
Can someone explain me this code. thanks

public IEnumerable GetTheCars(bool returnReversed)
{
   if(returnReversed)
   {
     for(int i=cars.Length; i!=0; i--)
     {
        yield return cars[i-1]; //this line makes me confused
     }
   }
   else {...}
}

Answer 1

You indicated in your comments that you need an explanation of how the reverse ordering works.

   for(int i=cars.Length; i!=0; i--)
   {
        yield return cars[i-1]; //this line makes me confused
   }

Let’s say you have 4 cars in your list.

Your for loop starts at a value of cars.Length, which will be 4. For each iteration it decrements by 1. It will continue doing this while the i!=0 condition is met. So, the loop will iterate with the following values of i: 4, 3, 2, 1.

If i is used as the element index for your array/list, then you will receive cars[4], cars[3], cars[2], cars[1] (reverse order!). But because arrays in C# start at 0 (and not 1), you need to subtract 1 when accessing the elements: cars[i-1].