How can I update the current line in a C# Windows Console App?

If you print only "\r" to the console the cursor goes back to the beginning of the current line and then you can rewrite it. This should do the trick:

for(int i = 0; i < 100; ++i)
{
    Console.Write("\r{0}%   ", i);
}

Notice the few spaces after the number to make sure that whatever was there before is erased.
Also notice the use of Write() instead of WriteLine() since you don't want to add an "\n" at the end of the line.

You can use Console.SetCursorPosition to set the position of the cursor and then write at the current position.

Here is an example showing a simple "spinner":

static void Main(string[] args)
{
    var spin = new ConsoleSpinner();
    Console.Write("Working....");
    while (true) 
    {
        spin.Turn();
    }
}

public class ConsoleSpinner
{
    int counter;

    public void Turn()
    {
        counter++;        
        switch (counter % 4)
        {
            case 0: Console.Write("/"); counter = 0; break;
            case 1: Console.Write("-"); break;
            case 2: Console.Write("\\"); break;
            case 3: Console.Write("|"); break;
        }
        Thread.Sleep(100);
        Console.SetCursorPosition(Console.CursorLeft - 1, Console.CursorTop);
    }
}

Note that you will have to make sure to overwrite any existing output with new output or blanks.

Update: As it has been criticized that the example moves the cursor only back by one character, I will add this for clarification: Using SetCursorPosition you may set the cursor to any position in the console window.

Console.SetCursorPosition(0, Console.CursorTop);

will set the cursor to the beginning of the current line (or you can use Console.CursorLeft = 0 directly).

So far we have three competing alternatives for how to do this:

Console.Write("\r{0}   ", value);                      // Option 1: carriage return
Console.Write("\b\b\b\b\b{0}", value);                 // Option 2: backspace
{                                                      // Option 3 in two parts:
    Console.SetCursorPosition(0, Console.CursorTop);   // - Move cursor
    Console.Write(value);                              // - Rewrite
}

I've always used Console.CursorLeft = 0, a variation on the third option, so I decided to do some tests. Here's the code I used:

public static void CursorTest()
{
    int testsize = 1000000;

    Console.WriteLine("Testing cursor position");
    Stopwatch sw = new Stopwatch();
    sw.Start();
    for (int i = 0; i < testsize; i++)
    {
        Console.Write("\rCounting: {0}     ", i);
    }
    sw.Stop();
    Console.WriteLine("\nTime using \\r: {0}", sw.ElapsedMilliseconds);

    sw.Reset();
    sw.Start();
    int top = Console.CursorTop;
    for (int i = 0; i < testsize; i++)
    {
        Console.SetCursorPosition(0, top);        
        Console.Write("Counting: {0}     ", i);
    }
    sw.Stop();
    Console.WriteLine("\nTime using CursorLeft: {0}", sw.ElapsedMilliseconds);

    sw.Reset();
    sw.Start();
    Console.Write("Counting:          ");
    for (int i = 0; i < testsize; i++)
    {        
        Console.Write("\b\b\b\b\b\b\b\b{0,8}", i);
    }

    sw.Stop();
    Console.WriteLine("\nTime using \\b: {0}", sw.ElapsedMilliseconds);
}

On my machine, I get the following results:

Backspaces: 25.0 seconds

Carriage Returns: 28.7 seconds

SetCursorPosition: 49.7 seconds

Additionally, SetCursorPosition caused noticeable flicker that I didn't observe with either of the alternatives. So, the moral is to use backspaces or carriage returns when possible, and thanks for teaching me a faster way to do this, SO!

Update: In the comments, Joel suggests that SetCursorPosition is constant with respect to the distance moved while the other methods are linear. Further testing confirms that this is the case, however constant time and slow is still slow. In my tests, writing a long string of backspaces to the console is faster than SetCursorPosition until somewhere around 60 characters. So backspace is faster for replacing portions of the line shorter than 60 characters (or so), and it doesn't flicker, so I'm going to stand by my initial endorsement of \b over \r and SetCursorPosition.

You can use the \b (backspace) escape sequence to backup a particular number of characters on the current line. This just moves the current location, it does not remove the characters.

For example:

string line="";

for(int i=0; i<100; i++)
{
    string backup=new string('\b',line.Length);
    Console.Write(backup);
    line=string.Format("{0}%",i);
    Console.Write(line);
}

Here, line is the percentage line to write to the console. The trick is to generate the correct number of \b characters for the previous output.

The advantage of this over the \r approach is that if works even if your percentage output is not at the beginning of the line.

\r is used for these scenarios.
\r represents a carriage return which means the cursor returns to the start of the line.
That's why Windows uses \n\r as its new line marker.
\n moves you down a line, and \r returns you to the start of the line.

I just had to play with the divo's ConsoleSpinner class. Mine is nowhere near as concise, but it just didn't sit well with me that users of that class have to write their own while(true) loop. I'm shooting for an experience more like this:

static void Main(string[] args)
{
    Console.Write("Working....");
    ConsoleSpinner spin = new ConsoleSpinner();
    spin.Start();

    // Do some work...

    spin.Stop(); 
}

And I realized it with the code below. Since I don't want my Start() method to block, I don't want the user to have to worry about writing a while(spinFlag) -like loop, and I want to allow multiple spinners at the same time I had to spawn a separate thread to handle the spinning. And that means the code has to be a lot more complicated.

Also, I haven't done that much multi-threading so it's possible (likely even) that I've left a subtle bug or three in there. But it seems to work pretty well so far:

public class ConsoleSpinner : IDisposable
{       
    public ConsoleSpinner()
    {
        CursorLeft = Console.CursorLeft;
        CursorTop = Console.CursorTop;  
    }

    public ConsoleSpinner(bool start)
        : this()
    {
        if (start) Start();
    }

    public void Start()
    {
        // prevent two conflicting Start() calls ot the same instance
        lock (instanceLocker) 
        {
            if (!running )
            {
                running = true;
                turner = new Thread(Turn);
                turner.Start();
            }
        }
    }

    public void StartHere()
    {
        SetPosition();
        Start();
    }

    public void Stop()
    {
        lock (instanceLocker)
        {
            if (!running) return;

            running = false;
            if (! turner.Join(250))
                turner.Abort();
        }
    }

    public void SetPosition()
    {
        SetPosition(Console.CursorLeft, Console.CursorTop);
    }

    public void SetPosition(int left, int top)
    {
        bool wasRunning;
        //prevent other start/stops during move
        lock (instanceLocker)
        {
            wasRunning = running;
            Stop();

            CursorLeft = left;
            CursorTop = top;

            if (wasRunning) Start();
        } 
    }

    public bool IsSpinning { get { return running;} }

    /* ---  PRIVATE --- */

    private int counter=-1;
    private Thread turner; 
    private bool running = false;
    private int rate = 100;
    private int CursorLeft;
    private int CursorTop;
    private Object instanceLocker = new Object();
    private static Object console = new Object();

    private void Turn()
    {
        while (running)
        {
            counter++;

            // prevent two instances from overlapping cursor position updates
            // weird things can still happen if the main ui thread moves the cursor during an update and context switch
            lock (console)
            {                  
                int OldLeft = Console.CursorLeft;
                int OldTop = Console.CursorTop;
                Console.SetCursorPosition(CursorLeft, CursorTop);

                switch (counter)
                {
                    case 0: Console.Write("/"); break;
                    case 1: Console.Write("-"); break;
                    case 2: Console.Write("\\"); break;
                    case 3: Console.Write("|"); counter = -1; break;
                }
                Console.SetCursorPosition(OldLeft, OldTop);
            }

            Thread.Sleep(rate);
        }
        lock (console)
        {   // clean up
            int OldLeft = Console.CursorLeft;
            int OldTop = Console.CursorTop;
            Console.SetCursorPosition(CursorLeft, CursorTop);
            Console.Write(' ');
            Console.SetCursorPosition(OldLeft, OldTop);
        }
    }

    public void Dispose()
    {
        Stop();
    }
}

Explicitly using a Carrage Return (\r) at the beginning of the line rather than (implicitly or explicitly) using a New Line (\n) at the end should get what you want. For example:

void demoPercentDone() {
    for(int i = 0; i < 100; i++) {
        System.Console.Write( "\rProcessing {0}%...", i );
        System.Threading.Thread.Sleep( 1000 );
    }
    System.Console.WriteLine();    
}

    public void Update(string data)
    {
        Console.Write(string.Format("\r{0}", "".PadLeft(Console.CursorLeft, ' ')));
        Console.Write(string.Format("\r{0}", data));
    }

From the Console docs in MSDN:

You can solve this problem by setting the TextWriter.NewLine property of the Out or Error property to another line termination string. For example, the C# statement, Console.Error.NewLine = "\r\n\r\n";, sets the line termination string for the standard error output stream to two carriage return and line feed sequences. Then you can explicitly call the WriteLine method of the error output stream object, as in the C# statement, Console.Error.WriteLine();

So - I did this:

Console.Out.Newline = String.Empty;

Then I am able to control the output myself;

Console.WriteLine("Starting item 1:");
    Item1();
Console.WriteLine("OK.\nStarting Item2:");

Another way of getting there.

This works if you want to make generating files look cool .

                int num = 1;
                var spin = new ConsoleSpinner();
                Console.ForegroundColor = ConsoleColor.Green;
                Console.Write("");
                while (true)
                {
                    spin.Turn();
                    Console.Write("\r{0} Generating Files ", num);
                    num++;
                }

And this is the method that i got from some answer below and modified it

public class ConsoleSpinner
    {
        int counter;

        public void Turn()
        {
            counter++;
            switch (counter % 4)
            {
                case 0: Console.Write("."); counter = 0; break;
                case 1: Console.Write(".."); break;
                case 2: Console.Write("..."); break;
                case 3: Console.Write("...."); break;
                case 4: Console.Write("\r"); break;
            }
            Thread.Sleep(100);
            Console.SetCursorPosition(23, Console.CursorTop);
        }
    }

Here's another one :D

class Program
{
    static void Main(string[] args)
    {
        Console.Write("Working... ");
        int spinIndex = 0;
        while (true)
        {
            // obfuscate FTW! Let's hope overflow is disabled or testers are impatient
            Console.Write("\b" + @"/-\|"[(spinIndex++) & 3]);
        }
    }
}

If you want update one line, but the information is too long to show on one line, it may need some new lines. I've encountered this problem, and below is one way to solve this.

public class DumpOutPutInforInSameLine
{

    //content show in how many lines
    int TotalLine = 0;

    //start cursor line
    int cursorTop = 0;

    // use to set  character number show in one line
    int OneLineCharNum = 75;

    public void DumpInformation(string content)
    {
        OutPutInSameLine(content);
        SetBackSpace();

    }
    static void backspace(int n)
    {
        for (var i = 0; i < n; ++i)
            Console.Write("\b \b");
    }

    public  void SetBackSpace()
    {

        if (TotalLine == 0)
        {
            backspace(OneLineCharNum);
        }
        else
        {
            TotalLine--;
            while (TotalLine >= 0)
            {
                backspace(OneLineCharNum);
                TotalLine--;
                if (TotalLine >= 0)
                {
                    Console.SetCursorPosition(OneLineCharNum, cursorTop + TotalLine);
                }
            }
        }

    }

    private void OutPutInSameLine(string content)
    {
        //Console.WriteLine(TotalNum);

        cursorTop = Console.CursorTop;

        TotalLine = content.Length / OneLineCharNum;

        if (content.Length % OneLineCharNum > 0)
        {
            TotalLine++;

        }

        if (TotalLine == 0)
        {
            Console.Write("{0}", content);

            return;

        }

        int i = 0;
        while (i < TotalLine)
        {
            int cNum = i * OneLineCharNum;
            if (i < TotalLine - 1)
            {
                Console.WriteLine("{0}", content.Substring(cNum, OneLineCharNum));
            }
            else
            {
                Console.Write("{0}", content.Substring(cNum, content.Length - cNum));
            }
            i++;

        }
    }

}
class Program
{
    static void Main(string[] args)
    {

        DumpOutPutInforInSameLine outPutInSameLine = new DumpOutPutInforInSameLine();

        outPutInSameLine.DumpInformation("");
        outPutInSameLine.DumpInformation("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb");


        outPutInSameLine.DumpInformation("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
        outPutInSameLine.DumpInformation("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb");

        //need several lines
        outPutInSameLine.DumpInformation("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
        outPutInSameLine.DumpInformation("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb");

        outPutInSameLine.DumpInformation("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
        outPutInSameLine.DumpInformation("bbbbbbbbbbbbbbbbbbbbbbbbbbb");

    }
}

i was looking for same solution in vb.net and i found this one and it's great.

however as @JohnOdom suggested a better way to handle the blanks space if previous one is larger than current one..

i make a function in vb.net and thought someone could get helped ..

here is my code:

Private Sub sPrintStatus(strTextToPrint As String, Optional boolIsNewLine As Boolean = False)
    REM intLastLength is declared as public variable on global scope like below
    REM intLastLength As Integer
    If boolIsNewLine = True Then
        intLastLength = 0
    End If
    If intLastLength > strTextToPrint.Length Then
        Console.Write(Convert.ToChar(13) & strTextToPrint.PadRight(strTextToPrint.Length + (intLastLength - strTextToPrint.Length), Convert.ToChar(" ")))
    Else
        Console.Write(Convert.ToChar(13) & strTextToPrint)
    End If
    intLastLength = strTextToPrint.Length
End Sub

I was doing a search for this to see if the solution I wrote could be optimised for speed. What I wanted was a countdown timer, not just updating the current line. Here's what I came up with. Might be useful to someone

            int sleepTime = 5 * 60;    // 5 minutes

            for (int secondsRemaining = sleepTime; secondsRemaining > 0; secondsRemaining --)
            {
                double minutesPrecise = secondsRemaining / 60;
                double minutesRounded = Math.Round(minutesPrecise, 0);
                int seconds = Convert.ToInt32((minutesRounded * 60) - secondsRemaining);
                Console.Write($"\rProcess will resume in {minutesRounded}:{String.Format("{0:D2}", -seconds)} ");
                Thread.Sleep(1000);
            }
            Console.WriteLine("");

Inspired by @E.Lahu Solution, implementation of a bar progress with percentage.

public class ConsoleSpinner
{
    private int _counter;

    public void Turn(Color color, int max, string prefix = "Completed", string symbol = "■",int position = 0)
    {
        Console.SetCursorPosition(0, position);
        Console.Write($"{prefix} {ComputeSpinner(_counter, max, symbol)}", color);
        _counter = _counter == max ? 0 : _counter + 1;
    }

    public string ComputeSpinner(int nmb, int max, string symbol)
    {
        var spinner = new StringBuilder();
        if (nmb == 0)
            return "\r ";

        spinner.Append($"[{nmb}%] [");
        for (var i = 0; i < max; i++)
        {
            spinner.Append(i < nmb ? symbol : ".");
        }

        spinner.Append("]");
        return spinner.ToString();
    }
}


public static void Main(string[] args)
    {
        var progressBar= new ConsoleSpinner();
        for (int i = 0; i < 1000; i++)
        {
            progressBar.Turn(Color.Aqua,100);
            Thread.Sleep(1000);
        }
    }

Here is my take on s soosh's and 0xA3's answers. It can update the console with user messages while updating the spinner and has an elapsed time indicator aswell.

public class ConsoleSpiner : IDisposable
{
    private static readonly string INDICATOR = "/-\\|";
    private static readonly string MASK = "\r{0} {1:c} {2}";
    int counter;
    Timer timer;
    string message;

    public ConsoleSpiner() {
        counter = 0;
        timer = new Timer(200);
        timer.Elapsed += TimerTick;
    }

    public void Start() {
        timer.Start();
    }

    public void Stop() {
        timer.Stop();
        counter = 0;
    }

    public string Message {
        get { return message; }
        set { message = value; }
    }

    private void TimerTick(object sender, ElapsedEventArgs e) {
        Turn();
    }

    private void Turn() {
        counter++;
        var elapsed = TimeSpan.FromMilliseconds(counter * 200);
        Console.Write(MASK, INDICATOR[counter % 4], elapsed, this.Message);
    }

    public void Dispose() {
        Stop();
        timer.Elapsed -= TimerTick;
        this.timer.Dispose();
    }
}

usage is something like this:

class Program
{
    static void Main(string[] args)
    {
        using (var spinner = new ConsoleSpiner())
        {
            spinner.Start();
            spinner.Message = "About to do some heavy staff :-)"
            DoWork();
            spinner.Message = "Now processing other staff".
            OtherWork();
            spinner.Stop();
        }
        Console.WriteLine("COMPLETED!!!!!\nPress any key to exit.");

    }
}

The SetCursorPosition method works in multi-threading scenario, where the other two methods don't