Question

我在for循环中有一个嵌套的if / else语句来确定一个值是否对数组值有效。它返回所有值就好了，但是如果IF是正确的，它还会另外三次。我认为一旦它等于一次，就会停止，但我想我在这里错过了一些东西。

string sectionChoice;
int ticketQuantity;
double ticketPrice, totalCost;
string[] section = { "orchestra", "mezzanine", "balcony", "general" };
double[] price = { 125.25, 62.00, 35.75, 55.50 };
bool isValidSection = false;

sectionChoice = GetSection();
ticketQuantity = GetQuantity();

for (int x = 0; x < section.Length; ++x)
{
    if (sectionChoice == section[x])
    {
        isValidSection = true;
        ticketPrice = price[x];

        totalCost = CalcTicketCost(ticketPrice, ticketQuantity);
        Console.Write("\n\nTotal cost for the tickets are: {0:c2}", totalCost);
    }
    else
        Console.Write("\n\nInvalid entry, {0} does not exist", sectionChoice);
}

如果有效，则返回如下内容：

您的价格是32.50。条目无效，x不存在无效条目，x不存在无效条目，x不存在

Answer 1

您真正要做的是确定section是否包含特定值，如果有，则执行某些操作。只需直接检查：

if (section.Contains(sectionChoice))

您也不应该使用parallel arrays。不是有两个数组，而是一个价格，其中每个的索引处的对象“组合”等于一个值，看来你实际建模的是一种查找特定部分价格的方法。这最好使用Dictionary建模，可以轻松查找特定键的值。这里你的关键是部分，价值是它的价格。

Dictionary<string, decimal> ticketsPrices = new Dictionary<string, decimal>()
{
    {"orchestra", 125.25m},
    //...
};
bool isValidSection = false;

string sectionChoice = GetSection();
int ticketQuantity = GetQuantity();

if (ticketsPrices.ContainsKey(sectionChoice))
{
    isValidSection = true;
    decimal ticketPrice = ticketsPrices[sectionChoice];

    decimal totalCost = CalcTicketCost(ticketPrice, ticketQuantity);
    Console.Write("\n\nTotal cost for the tickets are: {0:c2}", totalCost);
}
else
    Console.Write("\n\nInvalid entry, {0} does not exsist", sectionChoice);

Answer 2

您要查找的关键字是break;

break将停止执行它所在的循环。如果你在嵌套循环中，它只能在最里面工作。

与此相反的是continue。 Continue停止迭代并移动到下一个迭代。

Here is an MSDN article explaining it more in depth

for (int x = 0; x < section.Length; ++x)
{
   if (sectionChoice == section[x])
   {
      isValidSection = true;
      ticketPrice = price[x];

      totalCost = CalcTicketCost(ticketPrice, ticketQuantity);
      Console.Write("\n\nTotal cost for the tickets are: {0:c2}", totalCost);
      break;
   }
   else
     Console.Write("\n\nInvalid entry, {0} does not exsist", sectionChoice);
 }

Answer 3

获取所选项目的索引，如下所示：

int i = section.IndexOf(sectionChoice);
if (i >= 0) {
    ticketPrice = price[i];
} else {
    // Not found!
}

但是，使用项目类

，您的代码会变得更加灵活

public class Section
{
    public string Name { get; set; }
    public decimal Price { get; set; }
}

使用此课程，您可以创建一个像这样的部分列表

List<Item> sections = new List<item> {
    new Section { Name = "orchestra", Price = 125.25 },
    new Section { Name = "mezzanine", Price = 62.00 },
    ...
};

现在您可以找到这样的部分：

Section section = sections.FirstOrDefault(s => s.Name == sectionChoice);
if (section != null ) ...

像这样，更容易向部分添加新属性。例如。您可以添加一些剩余的座位，而无需创建新阵列。

Answer 4

如果希望在满足if条件时停止迭代，则需要使用break语句中断循环：

for (int x = 0; x < section.Length; ++x)
{

    if (sectionChoice == section[x])
    {
        isValidSection = true;
        ticketPrice = price[x];

        totalCost = CalcTicketCost(ticketPrice, ticketQuantity);
        Console.Write("\n\nTotal cost for the tickets are: {0:c2}", totalCost);
        break;  // THIS IS THE IMPORTANT CHANGE
    }

}
if (!isValidSection) // TEST MOVED OUTSIDE OF LOOP
{
    Console.Write("\n\nInvalid entry, {0} does not exsist", sectionChoice);
}

Answer 5

您不希望报告每个匹配不匹配的选项无效：

for (int x = 0; x < section.Length; ++x)
{
    if (sectionChoice == section[x])
    {
        isValidSection = true;
        ticketPrice = price[x];

        totalCost = CalcTicketCost(ticketPrice, ticketQuantity);
        Console.Write("\n\nTotal cost for the tickets are: {0:c2}", totalCost);
        break;
     }
}

if (!isValidSection)
    Console.Write("\n\nInvalid entry, {0} does not exist", sectionChoice);

C＃嵌套if循环中的/ if

5 个答案: