C# Console - How to ReadLine() without a new line? ( or undo a \n or a vertical \b)

Question

I want to know if it is possible to get back to the last line when I'm at the beginning of the next line? (in C# Console, of course)

I mean Console.WriteLine() cause going to the next line and I want to stay in my line even after pressing enter. (And I think there isn't another way to ReadLine without going to the next line , is there?)

I found that Console.SetCursorPosition() can be useful, like below:

        int x, y;
        Console.WriteLine("Please enter the point's coordinates in this form (x,y):");
        Console.Write("(");
        x = Convert.ToInt32(Console.ReadLine());
        Console.SetCursorPosition(x.ToString().Length + 1, Console.CursorTop - 1);
        Console.Write(",");
        y = Convert.ToInt32(Console.ReadLine());
        Console.SetCursorPosition(x.ToString().Length + y.ToString().Length + 2, Console.CursorTop - 1);
        Console.WriteLine(")");

This seems to work fine but when I try to change Console.Write("("); into something like Console.Write("Point A=("), I need to change the the Console.SetCursorPosition() arguments every time.

Also it would be very helpful if I could move the cursor to the last character (except spaces) in the console buffer.(I think it would be easy if I could copy a specific line from console into a string.)

Thanks in advance.

Answer 1

How about using a simple helper class that fits your specific use case and helps make your code logic a bit more readable.

public class Prompt
{
    public struct CursorPosition
    {
        public int CursorLeft;
        public int CursorTop;
    }

    private CursorPosition _savedPosition;

    public Prompt Write(string prompt)
    {
        Console.Write(prompt);
        return this;
    }

    public Prompt Write(string promptFormat, params object[] args)
    {
        return Write(string.Format(promptFormat, args));
    }

    public Prompt WriteLine(string prompt)
    {
        Write(prompt);
        Console.WriteLine();
        return this;
    }

    public Prompt WriteLine(string promptFormat, params object[] args)
    {
        return WriteLine(string.Format(promptFormat, args));
    }

    public string ReadLine(bool advanceCursorOnSameLine = false, bool eraseLine = false)
    {
        if (advanceCursorOnSameLine || eraseLine)
        {
            SavePosition();
            if (eraseLine)
                WriteLine(new string(' ', Console.WindowWidth - _savedPosition.CursorLeft)).RestorePosition();
        }
        var input = Console.ReadLine();
        if (advanceCursorOnSameLine)
            RestorePosition(input.Length);
        return input;
    }

    public Prompt SavePosition()
    {
        _savedPosition = GetCursorPosition();
        return this;
    }

    public CursorPosition GetCursorPosition()
    {
        return new CursorPosition {
            CursorLeft = Console.CursorLeft,
            CursorTop = Console.CursorTop
        };
    }

    public Prompt RestorePosition(CursorPosition position, int deltaLeft = 0, int deltaTop = 0)
    {
        var left = Math.Min(Console.BufferWidth - 1, Math.Max(0, position.CursorLeft + deltaLeft));
        var right = Math.Min(Console.BufferHeight - 1, Math.Max(0, position.CursorTop + deltaTop));
        Console.SetCursorPosition(left, right);
        return this;
    }

    public Prompt RestorePosition(int deltaLeft = 0, int deltaTop = 0)
    {
        return RestorePosition(_savedPosition, deltaLeft, deltaTop);
    }
}

Which can then be used like this:

class Program
{
    public static void Main(params string[] args)
    {
        int x, y;
        var prompt = new Prompt();
        prompt.WriteLine("Please enter the point's coordinates in this form (x,y):");
        var savedPos = prompt.GetCursorPosition();
        while (true)
        {
            x = Convert.ToInt32(prompt.Write("(").ReadLine(true, true));
            y = Convert.ToInt32(prompt.Write(",").ReadLine(true));
            prompt.WriteLine(")");
            // do something with x and y

            var again = prompt.Write("More (Y):").ReadLine(true, true);
            if (!again.StartsWith("Y", StringComparison.OrdinalIgnoreCase))
                break;
            prompt.RestorePosition(savedPos);
        }
    }
}