How a make a text blink in C# Console Application

Question

I'm a newbie in C#

I have this Code

    FileStream D = new FileStream("C:/PersonalAssistant/RecentMeetingDetails.txt", FileMode.Open, FileAccess.Read);
    StreamReader DR = new StreamReader(D);
    DR.BaseStream.Seek(0, SeekOrigin.Begin);

    Console.ForegroundColor = ConsoleColor.Red;
    Console.WriteLine("ALERT! ALERT!! ALERT!!!");
    Console.WriteLine("\nYour Closest Appointment is on " + rd + " and has the following info");

    string data = DR.ReadLine();
    while (data != null)
    {
         Console.WriteLine(data);
         data = DR.ReadLine();
    }
    D.Close();
    DR.Close();

I want this code

    Console.WriteLine("ALERT! ALERT!! ALERT!!!");

to be blinking while the other details are being read from the file and displayed on the screen

I have tried this

   private static void WriteBlinkingText(string text, int delay)
   {
        bool visible = true;
        while (true)
        {
            Console.Write("\r" + (visible ? text : new String(' ', text.Length)));
            System.Threading.Thread.Sleep(delay);
            visible = !visible;
        }
   }

and change th console.writeline to

    WriteBlinkingText("ALERT! ALERT!! ALERT!!!",500);

it worked but the other details were not displayed...

Pls help me correct this code

You've got a `while(true)`, so it will run forever won't it? — Dominic Zukiewicz, Jun 11 '13 at 10:03
@TijesunimiPreciousAmesinlola: Just in case, see my simpler answer for red to white blinking. — Chibueze Opata, Jun 11 '13 at 11:04

score 4 · Answer 1 · answered Jun 11 '13 at 10:11

4

Root cause:

Actually you are handling everything in a single Thread.
The Thread gets blocked by the infinite loop i.e. while(true) {... } inside WriteBlinkingText() method.

Solution:

Create a separate Thread for handling the blinking text. While your Main Thread would continue with the rest of code execution.

answered Jun 11 '13 at 10:11

Santosh Panda

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Thanks for your reply but Pls can u give an example Code – Jun 11 '13 at 10:17
I don't really understand why this is being upvoted. The thread is clearly prevented from blocking with `Thread.Sleep();` – Chibueze Opata Jun 11 '13 at 12:46
@ChibuezeOpata Thread.Sleep() does not release the thread for other work. It merely makes it do nothing for a given number of milliseconds. – Martin Brown Jun 11 '13 at 16:13
The point is, he wants it to loop the message forever. Console programs always terminate when `Ctrl+C` is pressed. Saying the problem is the loop doesn't help. Since he wants to do a display, he can do all the action at once and then manipulate the output on a loop. – Chibueze Opata Jun 11 '13 at 17:44

Chibueze Opata · Answer 2 · 2013-06-11T11:02:40.230

I guess you're looking for this:

bool visible = true;
do
{
    //Press Ctrl + C to Quit
    string alert = visible ? "ALERT! ALERT!! ALERT!!!" : "";
    visible = !visible;
    Console.Clear();
    string details = File.ReadAllText(@"C:\PersonalAssistant\RecentMeetingDetails.txt");
    Console.Write("{0}\n{1}", alert, details);
    Thread.Sleep(100);
} while (true);

Or to achieve WHITE TO RED blinking

bool visible = true;
do
{
    //Press Ctrl + C to Quit
    string alert = "ALERT! ALERT!! ALERT!!!";
    Console.ForegroundColor = visible ? ConsoleColor.Red : ConsoleColor.White;
    visible = !visible;
    Console.Clear();
    string details = @"C:\PersonalAssistant\RecentMeetingDetails.txt";
    Console.WriteLine(alert);
    Console.ForegroundColor = ConsoleColor.White;
    Console.WriteLine(details);
    Thread.Sleep(100);
} while (true);

You can easily refactor this into a method:

private static void Blinker(string text, int milliseconds)
{
    bool visible = true;
    while(true)
    {
        //Press Ctrl + C to Quit
        string alert = visible ? "ALERT! ALERT!! ALERT!!!" : "";
        visible = !visible;
        Console.Clear();
        string details = File.ReadAllText(@"C:\PersonalAssistant\RecentMeetingDetails.txt");
        Console.Write("{0}\n{1}", alert, details);
        Thread.Sleep(milliseconds);
    }
}

Martin Brown · Accepted Answer · 2013-06-11T10:37:36.700

Sorry to say this but flashing text is probably not a sensible thing to be doing with a console application.

The console does not support this for you so you will have to implement it yourself. As the console will only write to where the cursor is, you will have to keep moving the cursor back to the start of Alert! write out what you want and then move it back to where it was. This is not going to be pretty.

If you did want to do this the best way would be to use a timer (System.Threading.Timer). The timer would allow the rest of the application to run while between changes to the flashing text. When the timer event happened you would need to save the cursor location, move to the Alert text, Write or Blank it and then set the cursor back to the saved position. While you are doing this you need to find some way to block the file write so that you don't end up with chunks of file written where "Alert! Alert! Alert!" should be.

Finally it should be noted that this technique is going to be very strange to anyone that decides to Pipe the output of your application to a file like this: C:>MyApplication.exe > output.txt

Something like this ought to do it:

class Program
{
  static System.Threading.Timer timer = new Timer(TimerCallback, null, System.Threading.Timeout.Infinite, 0);
  static int alertX;
  static int alertY;
  static bool alertDisplayed = false;
  static int cursorX;
  static int cursorY;
  static object consoleLock = new object();

  static void Main(string[] args)
  {
     FileStream D = new FileStream("C:/PersonalAssistant/RecentMeetingDetails.txt", FileMode.Open, FileAccess.Read);
     StreamReader DR = new StreamReader(D);
     DR.BaseStream.Seek(0, SeekOrigin.Begin);

     Console.ForegroundColor = ConsoleColor.Red;
     WriteFlashingText();
     lock (consoleLock)
     {
        Console.WriteLine("\nYour Closest Appointment is on " + rd + " and has the following info");
     }

     string data = DR.ReadLine();
     while (data != null)
     {
        lock (consoleLock)
        {
           Console.WriteLine(data);
        }
        data = DR.ReadLine();
     }
     D.Close();
     DR.Close();
  }

  static void WriteFlashingText()
  {
     alertX = Console.CursorLeft;
     alertY = Console.CursorTop;
     timer.Change(0, 200);
  }

  static void TimerCallback(object state)
  {
     lock (consoleLock)
     {
        cursorX = Console.CursorLeft;
        cursorY = Console.CursorTop;

        Console.CursorLeft = alertX;
        Console.CursorTop = alertY;

        if (alertDisplayed)
        {
           Console.WriteLine("Alert! Alert! Alert!");
        }
        else
        {
           Console.WriteLine("                    ");
        }
        alertDisplayed = !alertDisplayed;

        Console.CursorLeft = cursorX;
        Console.CursorTop = cursorY;
     }
  }
}

I really dont know much about System.Threading.Timer..Pls can u direct me to where i can read more? — , Jun 11 '13 at 10:38
If you type it into Google or Bing you will get plenty to read, but start here: http://msdn.microsoft.com/en-us/library/system.threading.timer.aspx Note Multi-Threading is definitely on the advanced topics list. — Martin Brown, Jun 11 '13 at 10:50
Hmmm, multithreading? I think this is a far-fetched solution. — Chibueze Opata, Jun 11 '13 at 11:03

Sébastien Garmier · Answer 4 · 2013-06-11T11:16:00.060

class Program {
    static void Main(string[] args) {
        blinkText t = new blinkText("TestTestTest", 500); //new blinkText object
        t.start(); //start blinking

        Thread.Sleep(5000); //Do your work here

        t.stop(); //When your work is finished, call stop() to stop the blinking text blinking

        Console.ReadKey();
    }
}

public class blinkText {
    public blinkText(string text, int delay) {
        this.text = text;
        this.delay = delay;
        this.startLine = Console.CursorTop; //line number of the begin of the text
        this.startColumn = Console.CursorLeft; //column number of the begin of the text
        Console.Write(this.text);
        visible = true;
    }
    public string text;
    public int delay;
    int startLine;
    int startColumn;

    bool visible;

    Timer t;

    public void start() {
        t = new Timer(delegate { //Timer to do work async
            int oldCursorX = Console.CursorLeft; //Save cursor position
            int oldCursorY = Console.CursorTop;  //to restore them later
            Console.CursorLeft = startLine; //change cursor position to
            Console.CursorTop = startColumn; //the begin of the text
            visible = !visible;
            if (visible) {
                Console.Write(text); //write text (overwrites the whitespaces)
            } else {
                ConsoleColor oldColor = Console.ForegroundColor; //change fore color to back color
                Console.ForegroundColor = Console.BackgroundColor; //(makes text invisible)
                Console.Write(text); //write invisible text(overwrites visible text)
                Console.ForegroundColor = oldColor; //restore the old color(makes text visible)
            }
            Console.CursorLeft = oldCursorX; //restore cursor position
            Console.CursorTop = oldCursorY;
        });
        t.Change(0, this.delay); //start timer
    }

    public void stop() {
        t.Change(0, -1); //stop timer
        int oldCursorX = Console.CursorLeft;
        int oldCursorY = Console.CursorTop;
        Console.CursorLeft = startLine;
        Console.CursorTop = startColumn;
        Console.Write(text); //display text visible
        Console.CursorLeft = oldCursorX;
        Console.CursorTop = oldCursorY;
        visible = true;
    }
}

I edited the answer. Now I made a class which calls an async timer to blink the text. So this will not block your programm. To show this, I made a Thread.Sleep(5000) after the text begins blinking. This could be your code which takes a while to finish. Then the text ends blinking.

This will block in the same way as Tijesunimi Precious Amesinlola's code will. The while(true) creates an infinite loop that never releases control to the code that writes the file out. — Martin Brown, Jun 11 '13 at 10:47
In the original question the task was to write a file out while the text is blinking. What is there in your solution to stop the file being written where the Alert is displayed? Don't you need some kind of locking in place to prevent a write to the Console on the other thread between setting the cursor location and writing the alert text? — Martin Brown, Jun 11 '13 at 12:31
Yea, thats right... I never worked with this but I suppose you can use the `lock` keyword. — Sébastien Garmier, Jun 11 '13 at 12:50

score -4 · Answer 5 · answered Apr 16 '17 at 20:11

Easiest but the messy way to do it is :

static void Blink()
{
    Console.Clear();
        string name = "Your Text";
        Console.WriteLine(name);
        Thread.Sleep(500); //Break
        Console.Clear();
        Thread.Sleep(500);
        Console.WriteLine(name);
        Thread.Sleep(500);
        Console.Clear();
        Thread.Sleep(500);
        Console.WriteLine(name);
        Thread.Sleep(500);
        Console.Clear();
        Thread.Sleep(500);
        Console.WriteLine(name);
        Thread.Sleep(500);
        Console.Clear();
        Thread.Sleep(500);
        Console.WriteLine(name);
        Thread.Sleep(500);
        Console.ReadKey();
}

How a make a text blink in C# Console Application

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