使用当前上下文中不存在的未分配局部变量

Question

I am trying to add the concessionItem price to a list. I can not access the variable after the for loop is finished, because it is out of scope. I've tried writing totalCost above the foreach loop as well, but then it is not accessible within the logic.

public void PayForConcessions()
        {
            foreach (ConcessionItem ci in concessionItems)
            {
                decimal totalCost;
                totalCost += ci.Price;
            }

            this.RemoveMoney(totalCost);
        }

Answer 1

you have to assign totalCost and move it before foreach loop

        decimal totalCost = 0m;
       foreach (ConcessionItem ci in concessionItems)
            {
              
                totalCost += ci.Price;
            }

Answer 2

decimal total cost; needs to be declared inside the method body, but above the loop:

public void PayForConcessions()
{
    // HERE
    decimal totalCost;

    foreach (...)
    {
        ...
    }
}

Answer 3

I've tried writing totalCost above the foreach loop as well,

I think you might have put it in the wrong place.. This should be fine:

    public void PayForConcessions()
    {
        decimal totalCost = 0;
        foreach (ConcessionItem ci in concessionItems)
        {
            totalCost += ci.Price;
        }
        this.RemoveMoney(totalCost);
    }

Basic rule of variable scoping; inside the same set of { } brackets, or any nested brackets within, below the point of declaration..

Answer 4

You can try using Linq and get rid of loop at all:

using System.Linq;

...

public void PayForConcessions() => 
  RemoveMoney(concessionItems.Sum(ci => ci.Price));