How to modify the previous line of console text?

Question

I'd like to achieve something like this:

Time consuming operation...OK
Another time consuming operation...
And another one, but it completed, so...OK

I displayed 3 line of text, each one related with a thread which can end sooner or later. But if the second one complete later than the third one, I'll get something like this:

Time consuming operation...OK
Another time consuming operation...
And another one, but it completed, so...OKOK

Which is of course unacceptable. I know how to go back in current line, but is there a way to go UP? I'd swear I've seen it somewhere, though it could be a Linux console :)

Forget it. See Far File Manager! It works in Windows console, it works even in PowerShell! How to make something like this? And the coolest part is it restores console state after exiting. So maybe I should ask - how to access console buffer directly? I assume I'll need some native code to do the trick, but maybe there's another way? I thought of clearing console with each update, but this seems like overkill. Or maybe it isn't? Will it blink?

Answer 1

You can move cursor wherever you want: Console.SetCursorPosition or use Console.CursorTop.

Console.SetCursorPosition(0, Console.CursorTop -1);
Console.WriteLine("Over previous line!!!");

Answer 2

Use a carriage return. This sample prints a single line, overwriting what was there before.

  Console.WriteLine();
  for (int i = 0; i <= 100; i++)
  {
    System.Threading.Thread.Sleep(10);
    Console.Write("\x000DProgress: " + i);
  }

This works as long as all your strings are less than 80 columns (or whatever your terminal buffer is set to).

Answer 3

Note: the following answer was originally edited into the question by the OP.

---

Here's complete solution with demo:

using System;
using System.Collections.Generic;
using System.Threading;

namespace PowerConsole {

    internal class Containers {

        internal struct Container {
            public int Id;
            public int X;
            public int Y;
            public string Content;
        }

        public static List<Container> Items = new List<Container>();

        private static int Identity = 0;

        public static int Add(string text) {
            var c = new Container();
            c.Id = Identity++;
            c.X = Console.CursorLeft;
            c.Y = Console.CursorTop;
            c.Content = text;
            Console.Write(text);
            Items.Add(c);
            return c.Id;
        }

        public static void Remove(int id) {
            Items.RemoveAt(id);
        }

        public static void Replace(int id, string text) {
            int x = Console.CursorLeft, y = Console.CursorTop;
            Container c = Items[id];
            Console.MoveBufferArea(
                c.X + c.Content.Length, c.Y,
                Console.BufferWidth - c.X - text.Length, 1,
                c.X + text.Length, c.Y
            );
            Console.CursorLeft = c.X;
            Console.CursorTop = c.Y;
            Console.Write(text);
            c.Content = text;
            Console.CursorLeft = x;
            Console.CursorTop = y;
        }

        public static void Clear() {
            Items.Clear();
            Identity = 0;
        }
    }

    internal class Program {
        private static List<Thread> Threads = new List<Thread>();

        private static void Main(string[] args) {
            Console.WriteLine("So we have some threads:\r\n");
            int i, id;
            Random r = new Random();
            for (i = 0; i < 10; i++) {
                Console.Write("Starting thread " + i + "...[");
                id = Containers.Add("?");
                Console.WriteLine("]");
                Thread t = new Thread((object data) => {
                    Thread.Sleep(r.Next(5000) + 100);
                    Console.ForegroundColor = ConsoleColor.Green;
                    Containers.Replace((int)data, "DONE");
                    Console.ResetColor();
                });
                Threads.Add(t);
            }
            Console.WriteLine("\n\"But will it blend?\"...");
            Console.ReadKey(true);
            i = 0;
            Threads.ForEach(t => t.Start(i++));
            Threads.ForEach(t => t.Join());
            Console.WriteLine("\r\nVoila.");
            Console.ReadKey(true);
        }
    }
}