How to implement a blinking label on a form

Timer timer = new Timer();
timer.Interval = 500;
timer.Enabled = false;

timer.Start();

if( messagesNum > oldMessagesNum)
  timer.Tick += new EventHandler( timer_Tick );
else
  timer.Tick -= timer_Tick;

void timer_Tick( object sender, EventArgs e )
{
   if(messageLabel.BackColor == Color.Black)
      messageLabel.BackColor = Color.Red;
   else
      messageLabel.BackColor = Color.Black;
}

Here is a pretty simple implementation that would work inside your form. You could also create a custom control with the same code and just throw the Timer.Start() into a method for that control.

Create your own UserControl for this, one that inherits from Label instead of from Control directly. Add a StartBlinking method, in which you start a Timer object whose tick event alters the style of the label (changing the BackgroundColor and ForegroundColor properties each time to create the blink effect).

You could also add a StopBlinking method to turn it off, or you could have your Timer stop itself after 5 seconds, perhaps.

The following is blinking using async and await

private async void Blink(){
    while (true){
        await Task.Delay(500);
        label1.BackColor = label1.BackColor == Color.Red ? Color.Green : Color.Red;
    }
}

I know this is a really old post, but anyone looking for something a little more versatile than the Boolean solutions posted may get some use out of the following:

using System.Diagnostics;
using System.Threading.Tasks;

private async void SoftBlink(Control ctrl, Color c1, Color c2, short CycleTime_ms, bool BkClr)
{
    var sw = new Stopwatch(); sw.Start();
    short halfCycle = (short)Math.Round(CycleTime_ms * 0.5);
    while (true)
    {
        await Task.Delay(1);
        var n = sw.ElapsedMilliseconds % CycleTime_ms;
        var per = (double)Math.Abs(n - halfCycle) / halfCycle;
        var red = (short)Math.Round((c2.R - c1.R) * per) + c1.R;
        var grn = (short)Math.Round((c2.G - c1.G) * per) + c1.G;
        var blw = (short)Math.Round((c2.B - c1.B) * per) + c1.B;
        var clr = Color.FromArgb(red, grn, blw);
        if (BkClr) ctrl.BackColor = clr; else ctrl.ForeColor = clr;
    }
}

Which you can call like such:

SoftBlink(lblWarning, Color.FromArgb(30, 30, 30), Color.Red,2000,false);
SoftBlink(lblSoftBlink, Color.FromArgb(30, 30, 30), Color.Green, 2000,true);