在开关盒状态下写入开关盒状态的可能性？

Question

我有这个代码以它应该的方式运行。但是，如果用户在插入第一个值后单击1,2或3，我希望实现额外的功能。正如您所看到的，如果用户第二次按下2，将显示名字的玩家列表（至少这是我的意图）。所以我的问题是，如果可以通过在前一个中插入switch-case条件来完成此操作？我尝试过这样的事情：请参阅下面的更多代码。

 var isValidMenuItem = false;

        while (!isValidMenuItem)
            isValidMenuItem = Menu();

        Console.WriteLine();
        Console.ReadKey(true);

    }

    private static bool Menu()
    {
        Console.WriteLine("You have now entered the 2017 Wimbledon tournament!" + "\n" + "\n");
        Console.Write("Choose one of the 6 options:" + "\n" + "Press 1 for Default tournament:" + "\n" + "Press 2 for Women's single:" + "\n" +
            "Press 3 for Men's single:" + "\n" + "Press 4 for Women's double:" + "\n" + "Press 5 for Men's double:" + "\n" +
            "Press 6 for Mix double:" + "\n" + "Insert your choice...: ");

        var userValue = Console.ReadKey().KeyChar;
        Console.WriteLine();

        switch (userValue)
        {
            case '1':
                Console.WriteLine("\n"+ "You have entered a default tournament");
                break;
            case '2':
                Console.WriteLine("\n" + "You have entered women's single");
                Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" + 
                    "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
                break;
            case '3':
                Console.WriteLine("\n" + "You have entered men's single");
                Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" +
                    "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
                break;
            case '4':
                Console.WriteLine("\n" + "You have entered women's double");
                Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" +
                    "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
                break;
            case '5':
                Console.WriteLine("\n" + "You have entered men's double");
                Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" +
                    "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
                break;
            case '6':
                Console.WriteLine("\n" + "You have entered mix double");
                Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" +
                    "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
                break;
            default:
                Console.WriteLine("\n" + "Sorry! You have to choose one of the 6 tournament options");
                return false;
        }

像这样：......但它似乎不起作用？你们有什么想法吗？

         case '2':
                Console.WriteLine("\n" + "You have entered women's single");
                Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" + 
                    "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
                {
                    switch (userValue)
                    {
                        case '1':
                            Console.WriteLine("Hello");
                            break;
                    }
                    break;
                }

Answer 1

switch语句本身应该没问题。

问题在于变量userValue。您只评估var userValue = Console.ReadKey().KeyChar;一次，因此该值设置为该一个键值。

例如，在您的示例中，外部switch语句输入case'2'，因为这是userValue设置的内容。但是，当输入内部switch语句时，它使用相同的值AGAIN，因为ReadKey（）函数不会再次计算。 那么你的switch语句会将“userValue”视为2，甚至根本没有期待或等待任何输入，所以它就会掉出开关。

在这里编辑： 你可以再次调用ReadKey（）函数来解决这个问题，或者使用第二个变量：

//Inner switch statement:
//{ (bracket is redundant)
    userValue = Console.ReadKey().KeyChar;
    switch (userValue)
    {
        // switch body here...
    }
//}

Answer 2

您的代码中有两件事

第一

如果您的开关值与代码中的开关值相同，则无法工作，因为一个变量只能有一个值。

第二

删除括号

case '2':
                Console.WriteLine("\n" + "You have entered women's single");
                Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" + 
                    "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
                //{          <- remove
                    switch (userValue)
                    {
                        case '1':
                            Console.WriteLine("Hello");
                            break;
                    }
                    break;
                //}          <- remove

Answer 3

在我看来，那里有一个额外的花括号？不是吗？不应该是：

  case '2':
            Console.WriteLine("\n" + "You have entered women's single");
            Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" + 
                "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
             switch (userValue)
             {
                 case '1':
                     Console.WriteLine("Hello");
                     break;
                 default
                     return false;
             }
             break;

Answer 4

您需要先重新读取该值。

case '2':
    Console.WriteLine("\n" + "You have entered women's single");
    Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" +
        "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
    userValue = Console.ReadKey().KeyChar;
    {
        switch (userValue)
        {
            case '1':
                Console.WriteLine("Hello");
                break;
        }
    }
    break;

Answer 5

除了损害可读性之外，将switch嵌套在另一个switch内也没问题。该语言完全支持它。

在你的情况下你的switch不起作用，因为你打开一个自进入外部开关后没有改变的变量，所以这个结构实际上没用。在输入嵌套开关之前添加代码以修改userValue，如下所示：

case '2':
    Console.WriteLine("\n" + "You have entered women's single");
    Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" + 
        "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
    var userChoice = Console.ReadKey().KeyChar; // <<<<<==== Add this line
    switch (userChoice) {
        case '1':
            Console.WriteLine("Hello");
            break;
    }
    break;

Answer 6

切换开关应该可以正常工作！

int x = 1;

    switch(x)
    {
        case 1: // Enters Here cause x = 1
            Console.WriteLine("test"); //prints
            switch(x) // x still = 1
            {
                case 1: //enters here cause x = 1
                Console.WriteLine("works"); //prints
                break;
            }
            break;
        default:
            Console.WriteLine("doesnt work");
            break;
    }

（输出将是：＆＃34;测试＆＃34;＆＃34;工作＆＃34;）

你恰好写得很奇怪＆＃34; {}＆＃34;，那是问题吗？

如果要输入不同的Switch案例，则必须更改开关（值）的值以输入不同的情况。

在你的情况下：

case '2':
            Console.WriteLine("\n" + "You have entered women's single");
            Console.Write("Press 1 to start the tournament:" + "\n" + "Press 2 to list the players by first name:" + "\n" + 
                "Press 3 to list the players by last name:" + "\n" + "Insert your choice...: ");
            //Ask for a new input here = (NEWVALUE)
            switch (NEWVALUE)
            {
                case '1':
                Console.WriteLine("Hello");
                break;
            }
            break;

Answer 7

首先，您不需要嵌套开关。你必须连续选择两件事：

1. 锦标赛类型
2. 所选锦标赛类型的操作

因此，您可以为锦标赛类型创建枚举：

public enum TournamentType
{
    Default,
    SingleWomen,
    SingleMen,
    DoubleWomen,
    DoubleMen,
    DoubleMix
}

然后你需要选择选项。您可以在此处使用switch语句，但您也可以创建选项选择器类：

public class OptionSelector<T>
{
    private readonly List<Option> options = new List<Option>();
    public T SelectedOption { get; private set; }

    public OptionSelector<T> WithOption(T value, string title)
    {
        options.Add(new Option { Value = value, Title = title });
        return this;
    }

    public bool SelectOption()
    {
        if (!options.Any()) return true;            

        Console.WriteLine($"Choose one of the {options.Count} options:");    
        for(int i = 0; i < options.Count; i++)
            Console.WriteLine($" {i + 1} - {options[i].Title}");

        Console.Write("Your choice: ");
        var key = Console.ReadKey().KeyChar;
        Console.WriteLine();    
        int choice = key - '0';
        if (!Char.IsDigit(key) || choice == 0 || options.Count < choice) {
            Console.WriteLine($"Sorry, only digits 1..{options.Count} are allowed");
            return false;
        }

        SelectedOption = options[choice - 1].Value;
        return true;
    }

    private class Option {
        public T Value { get; set; }
        public string Title { get; set; }
    }
}

几行代码，但功能很好 - 这个类允许以流畅的方式构建一组选项，然后接受用户输入。如果输入有效，则可通过SelectedOption属性使用所选选项。否则将显示详细的错误消息。这里的好处是选项选择器是一个通用类。每个选项都可以是字面上的任何东西 - 整数，字符串，枚举值，甚至是方法。使用此类，您的所有代码都可以折叠为：

Console.WriteLine($"You have now entered the 2017 Wimbledon tournament!\n");
var tournamentTypeSelector = new OptionSelector<TournamentType>()
    .WithOption(TournamentType.Default, "Default tournament")
    .WithOption(TournamentType.SingleWomen, "Women's single")
    .WithOption(TournamentType.SingleMen, "Men's single")
    .WithOption(TournamentType.DoubleWomen, "Women's double")
    .WithOption(TournamentType.DoubleMix, "Mix double");

while (!tournamentTypeSelector.SelectOption()) { /*Console.Clear();*/ }

var tournamentType = tournamentTypeSelector.SelectedOption;
var actionSelector = new OptionSelector<Action>()
    .WithOption(() => StartTournament(tournamentType), "Start the tournament")
    .WithOption(() => Console.WriteLine("Not implemented"), "List players by first name")
    .WithOption(() => Console.WriteLine("Not implemented"), "List players by last name");

while (!actionSelector.SelectOption()) { /*Console.Clear();*/ }
actionSelector.SelectedOption(); // invoke selected action

宇呼！根本没有开关

此处的第一个选择器选择锦标赛类型。第二个选择器选择要调用的动作。这里的好处是你可以将参数传递给那些动作（例如锦标赛类型）。 Btw StartTournament是包含相应功能的方法：

private static void StartTournament(TournamentType tournamentType)
{
    // your code here
    Console.WriteLine("Tournament started");
}

检查Fiddle以查看其工作原理。请注意，小提琴不支持Console.ReadKey，因此您应该每次都按Enter键。