请帮助我对下面的 if 语句感到非常困惑

Question

我希望用户输入一个数字，但如果它低于零，我想显示一条错误消息，然后循环并询问用户另一个数字。这是我现在的代码。

  // this determines what the loop does.
for (int CustPos = 0; CustPos < LineNum; CustPos = CustPos + 1)  
{
   // this asks the user to enter the sales figures
   Console.Write("enter sales figures for" + customer[CustPos] + "  "); 
   // this is user's input is read in and stored.
   sales_figures[CustPos] = Double.Parse(Console.ReadLine()); 

   if (sales_figures[CustPos] < MIN_SALES_FIGURE) //True - continue
   {
      Console.WriteLine("");
      Console.WriteLine("entry invalid");
      Console.WriteLine("enter another value");
   }
   else//FALSE -> Go back to start of loop
   {
       Console.WriteLine("");
   }


   //this section displays the cust name, sales figure 70/30.
   Console.WriteLine(" ");
   fee_payable[CustPos] = (sales_figures[CustPos] / 100.0) 
               * licence_fee_in_percent[CustPos];
   Console.WriteLine(customer[CustPos] + 
                 " ----------- " + fee_payable[CustPos]);
   Console.WriteLine("Licence fee to be paid in GBP is :" + 
                 fee_payable[CustPos]);
   seventy_percent_value = ((fee_payable[CustPos] / 10.0) * 7);
   Console.WriteLine("70 percent of this fee is" + 
                  seventy_percent_value);
   thirty_percent_value = ((fee_payable[CustPos] / 10.0) * 3);
   Console.WriteLine("30 percent of this fee is" + 
                   thirty_percent_value);
   Console.WriteLine(" ");
}

。请帮助所有建议，我们将不胜感激！

谢谢

Answer 1

我认为 do-while 循环在这里会更好，伪代码：

userInput = -1
do
{
    userInput = Console.ReadLine
}
while (userInput <0)

Colin E.

Answer 2

您走在正确的道路上，只需查看关键字 继续

这是链接中的示例：

using System;
class ContinueTest 
{
    static void Main() 
    {
        for (int i = 1; i <= 10; i++) 
        {
            if (i < 9) 
            {
                continue;
            }
            Console.WriteLine(i);
        }
    }
}

注意：Continue 语句将控制传递给它出现的封闭迭代语句的下一个迭代。

Answer 3

if (sales_figures[CustPos] < MIN_SALES_FIGURE) //True - Continue                   //FALSE -> Go back to start of loop

实际上，这里没有任何代码可以使其返回到循环的开头。

我建议您先将其全部写为伪代码，然后将其转换为代码：

if (number entered is too low)
    then restart loop
    otherwise carry on

Answer 4

您需要的不是 if，而是 while：

while( sales_figure[CustPos] < 0 )
{
    Console.Write("enter sales figures for" + customer[CustPos] + "  ");

    sales_figures[CustPos] = Double.Parse(Console.ReadLine());
}

这保证了它将不断提示，直到他们输入大于零的值。

继续，不做你想做的事。继续意味着“继续并忽略此迭代”，这意味着您对该客户的值不正确。

Answer 5

将 WHILE 循环与 IF 结合使用：

continueflag = 0;
while (continueflag == 0)
{
    sales_figures[CustPos] = Double.Parse(Console.ReadLine());

    Console.WriteLine("");

    if (sales_figures[CustPos] >= MIN_SALES_FIGURE) {
        Console.WriteLine("entry invalid");
        Console.WriteLine("enter another value");
    } else continueflag = 1;
}