在循环外声明的 C# 变量在循环中被赋值但得到 'Unassigned' 编译错误

Question

我正在处理类作业，但无法编译。对于 multiplierString 和 MultiplcandString，我不断收到 “Use of unassigned local variable”。它们在 main 的顶部声明，但它似乎没有在 while 循环内为它们赋值。如果我在循环外强制一个值，错误就会消失。非常感激任何的帮助。谢谢。

这是怎么回事？

static void Main()
{

    bool goodInput = false;
    ConsoleKeyInfo cki;
    string multiplicandString;
    string multiplierString;
    string endProduct;
    string prompt;
    string response;
    Int64 TryNumber;

    prompt = "This program will multiply two numbers of reasonable length.";
    Console.WriteLine(prompt);
    Console.WriteLine();
    prompt = "Press the Escape (Esc) key to quit or any other key to continue.";
    cki = Console.ReadKey();

    if (cki.Key != ConsoleKey.Escape)
    {
        while (!goodInput)
        {
            prompt = "Please provide the multiplicand: ";
            Console.WriteLine(prompt);
            response = Console.ReadLine();

            if (Int64.TryParse(response, out TryNumber))
            {
                goodInput = true;
                multiplicandString = "a"; //TryNumber.ToString();
            }
            else
            {
                Console.WriteLine();
                prompt = "Invalid multiplicand entry. It must be all numbers.\a";
                Console.WriteLine(prompt);
                prompt = "Please try again.";
                Console.WriteLine(prompt);
            } // end if Int64.TryParse
        } // end while ! goodInput

        goodInput = false;

        while (!goodInput)
        {
            prompt = "Please provide the multiplier: ";
            Console.WriteLine(prompt);
            response = Console.ReadLine();

            if (Int64.TryParse(response, out TryNumber))
            {
                goodInput = true;
                multiplierString = "a"; //TryNumber.ToString();
            }
            else
            {
                Console.WriteLine();
                prompt = "Invalid multiplier entry. It must be all numbers.\a";
                Console.WriteLine(prompt);
                prompt = "Please try again.";
                Console.WriteLine(prompt);
            } // end if Int64.TryParse
        } // end while ! goodInput
          //multiplierString = "a"; //TryNumber.ToString();

        endProduct = MultiplyByRectangle(multiplicandString, multiplierString);

        Console.WriteLine("The result of the calculation is:");
        Console.WriteLine("\t" + endProduct);

    } // end Main()

Answer 1

C# 需要明确分配变量。意思是，变量必须先设置一个初始值，然后才能读取它。