尝试使用无效输入（C＃）循环切换开关

Question

Anyway I don't know how I'm supposed to go about doing this... in my application I need to have the switch repeat itself if there's an invalid input. All the application does is exit as soon as I enter a different result. Here's my code:

string str = Console.ReadLine(); 
char option = char.Parse(str);
//Need to repeat this switch:
switch (option)
{
    case 'N':
        Console.WriteLine("Creating New App...");
        break;
    case 'L':
        Console.WriteLine("Loading App...");
        break;
    case 'O':
        Console.WriteLine("Loading Options...");
        break;
    case 'Q':
        Console.WriteLine("Exiting Application...");
        System.Environment.Exit(1);
        break;
    default:
        Console.WriteLine("Invalid input.");
        break;
}
Console.ReadLine();

Answer 1

You could make use of a while statement.

bool shouldRun = true;

while(shouldRun)
{
    switch (option)
    {
        case 'N':
            Console.WriteLine("Creating New App...");
            shouldRun = false;
            break;
        case 'L':
            Console.WriteLine("Loading App...");
            shouldRun = false;
            break;
        case 'O':
            Console.WriteLine("Loading Options...");
            shouldRun = false;
            break;
        case 'Q':
            Console.WriteLine("Exiting Application...");
            System.Environment.Exit(1);
            break;
        default:
            Console.WriteLine("Invalid input.");
            shouldRun = true;
            break;
    }
}

Answer 2

Put the switch in a loop

bool invalidInput = true;

while (invalidInput)
{
    string str = Console.ReadLine(); 
    char option = char.Parse(str);

    switch (option)
    {
        case 'N':
            Console.WriteLine("Creating New App...");
            invalidInput = false;
            break;
        case 'L':
            Console.WriteLine("Loading App...");
            invalidInput = false;
            break;
        case 'O':
            Console.WriteLine("Loading Options...");
            invalidInput = false;
            break;
        case 'Q':
            Console.WriteLine("Exiting Application...");
            System.Environment.Exit(1);
            break;
        default:
            Console.WriteLine("Invalid input.");
            break;
    }
}

Answer 3

To repeat the switch you need to use one loop.I think you are looking for something like the following:

    bool ExitFlag = true;
    while (ExitFlag)
    {
        ExitFlag = false;
        switch (option)
        {
            case 'N':
                Console.WriteLine("Creating New App...");
                break;
            case 'L':
                Console.WriteLine("Loading App...");
                break;
            case 'O':
                Console.WriteLine("Loading Options...");
                break;
            case 'Q':
                Console.WriteLine("Exiting Application...");
                System.Environment.Exit(1);
                break;
            default:
                Console.WriteLine("Invalid input.");
                ExitFlag = true;
                break;
        }
    }

Note How It Works :

Let the ExitFlag be a Boolean value that controls the while loop( stop iteration and exit the while when ExitFlag is false). and are initialized with true . in each time the control enters into the while the flag is set to false so that we can avoid setting it false in multiple cases. The flag will set to true only when the default case is executed(ie., the invalid output) hence the loop repeats in this condition only.

Answer 4

You can use the Goto: label option in C#.

Ref: https://msdn.microsoft.com/en-us/library/13940fs2.aspx

    ReadAgain:
    string str = Console.ReadLine(); 
    char option = char.Parse(str);

    //The switch itself:
    switch (option)
    {
        case 'N':
            Console.WriteLine("Creating New App...");
            break;
        case 'L':
            Console.WriteLine("Loading App...");
            break;
        case 'O':
            Console.WriteLine("Loading Options...");
            break;
        case 'Q':
            Console.WriteLine("Exiting Application...");
            System.Environment.Exit(1);
            break;
        default:
            Console.WriteLine("Invalid input.");
            goto ReadAgain;
            break;
    }
    Console.ReadLine();