在控制台应用程序中验证多个用户输入

Question

我是 C# 的新手，想知道如何验证用户输入以满足以下要求：

• 必须是十进制类型。如果不是，它应该要求用户输入一个十进制值。 （我相信我已经在下面的代码中介绍过）
• 还必须在特定范围内 (1 - 1,000,000)。如果不是，则应要求用户输入正确范围内的数字

考虑到我将有多个用户输入以相同的方式进行验证，这样做最有效的方法是什么。

decimal balance;
Console.Write("Starting Balance: $");
while (!decimal.TryParse(Console.ReadLine(), out balance))
{
    Console.Write("Please enter a valid decimal value: $");
}

以下编辑

这个怎么样？

decimal balance;
Console.Write("Starting Balance: $");
while(true)
{
    if (!decimal.TryParse(Console.ReadLine(), out balance))                
        Console.Write("Please enter a valid decimal value: $");
    else if (balance < 1 || balance > 100)
        Console.Write("Please enter an amount between 1 and 100: ");
    else
        break;                
}
Console.WriteLine("Balance entered is: " + balance.ToString("n"));

return val; 行给了我一个错误，所以我忽略了它，但上面的方法似乎有效？

Answer 1

我会尝试类似：

decimal GetUserInput(string inputQuery, decimal min, decimal max)
{
  Console.Write(inputQuery);
  decimal val;
  while(true)
  {
    if(!decimal.TryParse(Console.ReadLine(), out val))
      Console.Write("Please enter a valid decimal value: $");
    else if(val < min || val > max)
      Console.Write("Please enter an amount between " + min + " and " + max + ": $");
    else // the value is a decimal AND it's correct
      break;
  } 
  return val;
}

然后像这样使用它：

var startingBalance = GetUserInput("Starting Balance: $", 1, 100000);
var endingBalance = GetUserInput("Ending Balance: $", 1, 100000);
//...

如果您的最小值和最大值是固定的，那么您不能将它们作为参数传递并使用固定检查。如果需要，您还可以避免传入查询 : $，但我将把它留给您

更新

return val 行给你一个错误的原因是因为你将它内联（可能在void 返回函数中）。我所做的是创建一个函数，因为您指定它需要可重用。

所以在你的程序中，你需要创建一个单独的函数......你的程序看起来像这样：

class Program
{
    // We're declaring this function static so you can use it without an instance of the class
    // This is a function, so it can be called multiple times, with different arguments
    static decimal GetUserInput(string inputQuery, decimal min, decimal max)
    {
      // Write the argument "inputQuery" to console
      Console.Write(inputQuery);
      decimal val;

      // Loop indefinitely
      while(true)
      {
        // Read from console into a decimal "val"
        if(!decimal.TryParse(Console.ReadLine(), out val))
          // It was not a correct decimal, so write the prompt
          Console.Write("Please enter a valid decimal value: $");
        // It was a correct decimal
        else if(val < min || val > max)
          // But not in range, so write a different prompt
          Console.Write("Please enter an amount between " + min + " and " + max + ": $");
        // It was a decimal and within range
        else
          // so we break the infinite loop and exit after the "}"
          break;

        // If we have got to this point (we didn't hit the "break"),
        // it was either not a decimal or it wasn't within range, 
        // so it'll loop again and ask for a value from console again.
        // The prompt was already written above (in the "ifs")

      } 
      // We got out of the while(true){} loop, so it means we hit "break"
      // above, and that means "val" contains a correct value (decimal and
      // within range), so we return it to the caller
      return val;
    }

    static void Main()
    {
      // Your original code went here, but see how my function is *outside* function Main()

      // You use my function (GetUserInput) here:
      var startingBalance = GetUserInput("Starting Balance: $", 1, 100000);
      var endingBalance = GetUserInput("Ending Balance: $", 1, 100000);

      // Then with the returned values (stored in "startingBalance"
      // and "endBalance"), you can do what you want:
      Console.WriteLine("Starting balance was: " + startingBalance.ToString("n"));
    }
}

我已经对整个程序进行了修改，以便您可以在线测试并进行更改：https://dotnetfiddle.net/HiwwIP

Answer 2

如果我是你，我会这样做：

        bool isInvalid, isOutOfRange;
        decimal balance = 0;
        isOutOfRange = true;
        do
        {
            string input = Console.ReadLine();
            isInvalid = !Decimal.TryParse(input, out balance);
            if (!isInvalid)
            {
                // use balance<=1 if 1 should not be included
                // use balance>=1000000 if 1000000 should not be included
                isOutOfRange = (balance < 1 || balance > 1000000);
            }
            if (isInvalid)
            {
                Console.WriteLine("Please enter a valid decimal value: $");
            }
            else if (isOutOfRange)
            {
                Console.WriteLine("Please enter value between 1 and 1000000: $");
            }

        } while (isInvalid || isOutOfRange);
        Console.WriteLine("{0}, That is a valid value!", balance.ToString());
        Console.ReadKey();

当然，您可以通过消除bool 定义并直接调用函数来实现快捷方式；但为了清楚起见，我写得很详细，因为你表示你是“相当新的”。