错误：CS1503 参数 1 和错误：CS0019 '=='

Question

我们目前正在学习一个类中的函数、参数、参数，所以我想保持相同的格式，因为“十进制价格”和“十进制金额”将被输入到函数定义中

我尝试了不同的方法将“小数”转换为“字符串”，以防止用户输入字符而不是小数，但我不知道为什么它不起作用

由于“金额”是decimal，因此需要将其转换为string 才能运行(amount == string.Empty)，但作为第一个问题，我无法弄清楚。

        decimal price; 
        decimal amount; 



        Console.Write("What is the price?"); 
        price = decimal.Parse(Console.ReadLine()); 


        double pricenumber;

        while (!double.TryParse(price, out pricenumber)) //error here 
        {
            Console.WriteLine("You've not entered a price.\r\nPlease enter a price");
            price = decimal.Parse(Console.ReadLine());

        }

        Console.Write("How many were you planning on purchasing?"); 

        amount = decimal.Parse(Console.ReadLine()); 

        while (amount == string.Empty) //error here
        {
            Console.WriteLine("You cannot leave this blank.\r\nPlease enter how many are needed:");
            amount = decimal.Parse(Console.ReadLine());
        }

Answer 1

您的代码中存在一些逻辑缺陷，您必须加以修复。请看cmets：

Console.Write("What is the price?"); 
price = decimal.Parse(Console.ReadLine()); // you're already parsing the user-input into
// a decimal. This is somewhat problematic, because if the user enters "foo" instead 
// of "123" the attempt to parse the input will fail

double pricenumber;
while (!double.TryParse(price, out pricenumber)) // the variable "price" already contains
// a parsed decimal. That's what you did some lines above. "TryParse" expects a string to
// be parsed whereas you're committing the parsed decimal
{
    Console.WriteLine("You've not entered a price.\r\nPlease enter a price");
    price = decimal.Parse(Console.ReadLine());
}

所以你应该做的是将用户输入保持为字符串，直到你尝试解析它：

Console.Write("What is the price?"); 
string input = Console.ReadLine(); // keep as string

double pricenumber;
while (!decimal.TryParse(input, out pricenumber))
{
    Console.WriteLine("You've not entered a price.\r\nPlease enter a price");
    input = Console.ReadLine();
}

---

您的其他尝试也是如此。再次，请查看 cmets：

Console.Write("How many were you planning on purchasing?"); 
amount = decimal.Parse(Console.ReadLine()); // you're already parsing the string into a
// decimal

while (amount == string.Empty) // as you can't compare a decimal with a string, this 
// creates an error
{
    Console.WriteLine("You cannot leave this blank.\r\nPlease enter how many are needed:");
    amount = decimal.Parse(Console.ReadLine());
}

你可以用上面的方法解决它：

Console.Write("How many were you planning on purchasing?"); 
input = Console.ReadLine(); // again, keep as string

while (!decimal.TryParse(input, out amount))
{
    Console.WriteLine("You cannot leave this blank.\r\nPlease enter how many are needed:");
    input = Console.ReadLine();
}

---

如果还有进一步优化的空间，您可以并且应该将该逻辑放入单独的方法中，因为代码几乎相同并且会导致重复。

private static decimal GetParsedInput(string question, string noticeOnFailed)
{
    Console.Write(question); 
    input = Console.ReadLine();

    decimal result;
    while (!decimal.TryParse(input, out result))
    {
        Console.WriteLine(questionOnFailed);
        input = Console.ReadLine();
    }

    return result;
}

用法：

decimal price = GetParsedInput(
    "What is the price?", 
    "You've not entered a price.\r\nPlease enter a price:");
decimal amount = GetParsedInput(
    "How many were you planning on purchasing?", 
    "You cannot leave this blank.\r\nPlease enter how many are needed:");

Answer 2

试试这个：

string price;
        string amount;



        Console.Write("What is the price?");
        price = Console.ReadLine();


        double pricenumber;

        while (!double.TryParse(price, out pricenumber)) 
        {
            Console.WriteLine("You've not entered a price.\r\nPlease enter a price");
            price = Console.ReadLine();

        }

        Console.Write("How many were you planning on purchasing?");

        double amountnumber;
        amount = Console.ReadLine();

        while (!double.TryParse(amount, out amountnumber)) 
        {
            Console.WriteLine("You cannot leave this blank.\r\nPlease enter how many are needed:");
            amount = Console.ReadLine();
        }

Answer 3

我想通了

我已经这样做了

{ public static decimal questions(string question)
    {
        Console.Write(question);
        string answer = Console.ReadLine();
       
        decimal result;
        while (!decimal.TryParse(answer, out result))
        {
            Console.WriteLine(question);
            answer = Console.ReadLine();
        }
        return result;
}

用法：

 string productcost = "How much does one " + productname + " cost? ";
 questions(productcost);

完美运行