Listen on ESC while reading Console line

问题

I want to read an users input into a string while still reacting on ESC press at any time, but without defining a system wide hotkey.

So when the user types e. g. "Test Name" but instead of confirming with ENTER presses ESC he should be led back into main menu.

Console.Write("Enter name: ")
if (Console.ReadLine().Contains(ConsoleKey.Escape.ToString()))
{
    goto MainMenu;
}
return Console.ReadLine();

Thats the simplest way I could think of, but since ESC is not seen by Console.ReadLine() it is not working.

Found a rather complex way to react on ESC when pressed before starting to enter text here, but I want it to work at any time.

回答1:

You will probably have to forego the use of ReadLine and roll your own using ReadKey:

static void Main(string[] args)
{
    Console.Clear();
    Console.Write("Enter your name and press ENTER.  (ESC to cancel): ");
    string name = readLineWithCancel();

    Console.WriteLine("\r\n{0}", name == null ? "Cancelled" : name);

    Console.ReadLine();
}

//Returns null if ESC key pressed during input.
private static string readLineWithCancel()
{
    string result = null;

    StringBuilder buffer = new StringBuilder();

    //The key is read passing true for the intercept argument to prevent
    //any characters from displaying when the Escape key is pressed.
    ConsoleKeyInfo info = Console.ReadKey(true);
    while (info.Key != ConsoleKey.Enter && info.Key != ConsoleKey.Escape)
    {
        Console.Write(info.KeyChar);
        buffer.Append(info.KeyChar);
        info = Console.ReadKey(true);
    } 

    if (info.Key == ConsoleKey.Enter)
    {
        result = buffer.ToString();
    }

    return result;
}

This code is not complete and may require work to make it robust, but it should give you some ideas.

回答2:

A bit improved version of Chris Dunaway's one :

    public static bool CancelableReadLine(out string value)
    {
        value = string.Empty;
        var buffer = new StringBuilder();
        var key = Console.ReadKey(true);
        while (key.Key != ConsoleKey.Enter && key.Key != ConsoleKey.Escape)
        {
            if (key.Key == ConsoleKey.Backspace && Console.CursorLeft > 0)
            {
                var cli = --Console.CursorLeft;
                buffer.Remove(cli, 1);
                Console.CursorLeft = 0;
                Console.Write(new String(Enumerable.Range(0, buffer.Length + 1).Select(o => ' ').ToArray()));
                Console.CursorLeft = 0;
                Console.Write(buffer.ToString());
                Console.CursorLeft = cli;
                key = Console.ReadKey(true);
            }
            else if (Char.IsLetterOrDigit(key.KeyChar) || Char.IsWhiteSpace(key.KeyChar))
            {
                var cli = Console.CursorLeft;
                buffer.Insert(cli, key.KeyChar);
                Console.CursorLeft = 0;
                Console.Write(buffer.ToString());
                Console.CursorLeft = cli + 1;
                key = Console.ReadKey(true);
            }
            else if (key.Key == ConsoleKey.LeftArrow && Console.CursorLeft > 0)
            {
                Console.CursorLeft--;
                key = Console.ReadKey(true);
            }
            else if (key.Key == ConsoleKey.RightArrow && Console.CursorLeft < buffer.Length)
            {
                Console.CursorLeft++;
                key = Console.ReadKey(true);
            }
            else
            {
                key = Console.ReadKey(true);
            }
        }

        if (key.Key == ConsoleKey.Enter)
        {
            Console.WriteLine();
            value = buffer.ToString();
            return true;
        }
        return false;
    }
}

I didn't test it much, but at least works for me.

回答3:

In case someone has the same problem. Found an solution by my own. Could be a little shorter, but at least it works:

                string name;
                char CurrentChar = ' ';                    
                do
                {
                    CurrentChar = Console.ReadKey().KeyChar;
                    if (CurrentChar != '\b')
                    {
                        name = name + CurrentChar;
                        if (CurrentChar == (char)13)
                        {
                            return name;
                        }
                    }
                    else if (Console.CursorLeft >= 14)
                    {
                        name = name.Remove(name.Length - 1);
                        Console.Write(" \b");
                    }
                    else
                    {
                        Console.CursorLeft = 14;
                    }

                } while (CurrentChar != (char)27);

回答4:

This is the simplest way:

Console.WriteLine("Press ESC to go to Main Menu");

while (!(Console.KeyAvailable && Console.ReadKey(true).Key == ConsoleKey.Escape))
{
    // your code here
}
goto MainMenu;

来源：https://stackoverflow.com/questions/31996519/listen-on-esc-while-reading-console-line