代码中出现的错误

Question

帮助，我不知道这个错误是什么

Console.WriteLine (num1 + " + " + num2 " = " answer);

这会返回四个错误（即使用monodevelop）

1. ）预期
2. ;预期
3. ;预期（是的，它出现两次）
4. 无效的表达式术语'）' 还有三个相似的行有相同的错误

这是整个代码

using System;

namespace CMD_test
{
class MainClass
{
    public static void Main (string[] args)
    {
        Start:
        double num1;
        double num2;
        double answer;

        Console.WriteLine ("What operation shall we use? Type:");
        Console.WriteLine ("A - for addition");
        Console.WriteLine ("S - for subtraction");
        Console.WriteLine ("M - for multiplication");
        Console.WriteLine ("D - for division");

        KeyPress:
        string key = Console.Read ();

        if (key == "A") {
            Console.WriteLine ("You chose addition");
            Console.Write ("What is the first number? ");
            num1 = Convert.ToDouble (Console.ReadLine ());
            Console.Write ("What is the second number? ");
            num2 = Convert.ToDouble (Console.ReadLine ());
            answer = num1 + num2;
            Console.WriteLine (num1 + " + " + num2 " = " answer);
        }
        if (key == "S") {
            Console.WriteLine ("You chose subtraction");
            Console.Write ("What is the first number? ");
            num1 = Convert.ToDouble (Console.ReadLine ());
            Console.Write ("What is the second number? ");
            num2 = Convert.ToDouble (Console.ReadLine ());
            answer = num1 - num2;
            Console.WriteLine (num1 + " - " + num2 " = " answer);
        }
        if (key == "M") {
            Console.WriteLine ("You chose multiplication");
            Console.Write ("What is the first number? ");
            num1 = Convert.ToDouble (Console.ReadLine ());
            Console.Write ("What is the second number? ");
            num2 = Convert.ToDouble (Console.ReadLine ());
            answer = num1 * num2;
            Console.WriteLine (num1 + " * " + num2 " = " answer);
        } else if (key == "D") {
            Console.WriteLine ("You chose division");
            Console.Write ("What is the first number? ");
            num1 = Convert.ToDouble (Console.ReadLine ());
            Console.Write ("What is the second number? ");
            num2 = Convert.ToDouble (Console.ReadLine ());
            answer = num1 / num2;
            Console.WriteLine (num1 + " / " + num2 " = " answer);
        } else {
            Console.WriteLine ("You pressed a wrong button! Please retry.");
            goto KeyPress;
        }

        Console.Write ("Do you want to do another operation? Y/N: ");

        string restart = Console.ReadLine ();
        if (restart == "Y") {
            Console.Clear ();
            goto Start;
        } else if (restart == "N") {
            Console.WriteLine ("Press any key to exit");
            Console.ReadKey ();
        }
    }
}
}

也许还有一些我不知道的其他错误

Answer 1

你的表达

Console.WriteLine (num1 + " + " + num2 " = " answer);

不是有效的，因为你已经错过了几个+的表达。将其更改为：

Console.WriteLine (num1 + " + " + num2 + " = " + answer);

并且它正确编译。更好的是，这样做，你就可以避免这样的拼写错误：

Console.WriteLine ("{0} + {1} = {2}", num1, num2, answer);

哦，除此之外，当你切换到C＃6时，你将能够做到这一点，这简化了事情：

Console.WriteLine ("{num1} + {num2} = {answer}");

Answer 2

Console.WriteLine (num1 + " + " + num2 " = " answer);

实际应该是

Console.WriteLine (num1 + " + " + num2 + " = " + answer);

你错过了两个加号。这就是它产生错误的原因 您的IDE已告诉您问题的实际位置。

此外，以这种方式连接字符串不是一个好习惯。 Console.WriteLine允许您使用字符串格式：

Console.WriteLine ("{0} + {1} = {2}", num1, num2, answer);

在这里阅读复合格式：
https://msdn.microsoft.com/en-us/library/txafckwd(v=vs.110).aspx

Answer 3

以下是您尝试做的一个示例。