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Posted 17 Jul 2006


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How to write a loading circle animation in .NET?

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4.92/5 (211 votes)
15 Feb 2007CPOL3 min read
A new kind of progress bar for .NET 2.0.

Sample Image - mrg_loadingcircle.jpg


When it's time to wait, we are used to seeing the classic blue progress bar. It is everywhere in Windows and many other applications. However, animations are getting more and more popular.

For example, when Firefox loads a page, a small spinning circle appears and shows you that the page is loading. Moreover, Microsoft also uses this kind of animation in the Windows Media Center, Encarta 2006, SQL Server Management Studio Express, etc.

So, why don't we use this concept to show to our users that our application is working and/or loading? Let's begin by the presentation of the component I developed.

Points of interest

Rotation speed

The LoadingCircle uses a timer, and it has two responsibilities: to determine the color of the next spoke, and to redraw the circle at a specified number of milliseconds. When you use the property RotationSpeed, you modify the timer's property named Interval. Higher the value is, slower will be the rotation. The default rotation speed is 80, so at every 80 milliseconds, the circle will be redrawn.

How to draw a spoke?

First of all, we need coordinates for each spoke. We use the function DrawLine of GDI+, which needs two points, the beginning and the end of the line.

So, let's review some simple math notions. In order to draw a perfect circle, you have to know the following trigonometry concept: the cosines of an angle in degrees give us the X and the sine gives us the Y.

The method GetCoordinate computes, for a specified radius and angle, the coordinates of a point.

private PointF GetCoordinate(PointF _objCircleCenter, 
               int _intRadius, double _dblAngle)
      PointF objPoint = new PointF();
      double dblAngle = Math.PI * _dblAngle / NUMBER_OF_DEGREES_HALF_CIRCLE;
      objPoint.X = _objCircleCenter.X + _intRadius * (float)Math.Cos(dblAngle);
      objPoint.Y = _objCircleCenter.Y + _intRadius * (float)Math.Sin(dblAngle);
      return objPoint;

The method DrawLine uses the coordinates computed by GetCoordinate, and draws a line with the two specified points and a color. Of course, we have to pass to this method the Graphics object of GDI+. As you can see, each line is rounded with the properties StartCap and EndCap of the Pen object.

private void DrawLine(Graphics _objGraphics, PointF _objPointOne, 
                      PointF _objPointTwo, 
                      Color _objColor, int _intLineThickness)
      using(Pen objPen = new Pen(new SolidBrush(_objColor), _intLineThickness))
            objPen.StartCap = LineCap.Round;
            objPen.EndCap = LineCap.Round;
            _objGraphics.DrawLine(objPen, _objPointOne, _objPointTwo);

How to use this component?

This component is quite easy to use. Once added to your toolbox, drag it to your form, and you are in business! Now, all you have to do is to play with the properties which change the look of the circle. Those are under the category "LoadingCircle" in the Properties panel. Also, you can change the Active property to true or false to see the animation running or not.

The component has the following properties.

  • Color - The color of an inactive spoke.
  • OuterCircleRadius - This property is the radius of the outer circle. The value of this property is supposed to be higher than the InnerCircleRadius value.
  • InnerCircleRadius - This property is the radius of the inner circle.
  • NumberSpoke - This property is the number of spokes.
  • Active - Defines if the component is animated or not. So, if tour treatment is in progress, this property should be set to true, otherwise false.
  • SpokeThickness - Thickness of the line in pixel.
  • RotationSpeed - Animation speed. Lower is the value, faster is the animation.


Finally, I wish you will find this component useful. I had fun writing it, and wish you will use it. Thanks for reading this article.

Revision history

  • June 17, 2006 : Initial release.
  • February 05, 2007 : Better color management (alpha blending)
  • February 10, 2007 : Presets defined in the control (MacOS X, Internet Explorer 7 and FireFox). A new control has been added: LoadingCircleToolStripMenuItem. This control is compatible with the StatusStrip! Supports transparency. Some minors bug corrections.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Martin Gagne
Web Developer
Canada Canada
Looking for an online tool which allows you to sort the content of your text file, remove duplicate lines as well as empty lines. Go take a look at my new website:

Comments and Discussions

GeneralVery nice Pin
ldyc4-Apr-07 5:50
Memberldyc4-Apr-07 5:50 
QuestionAnimation stops while long process executes Pin
jwhite046125-Mar-07 7:22
Memberjwhite046125-Mar-07 7:22 
AnswerRe: Animation stops while long process executes Pin
Martin Gagne26-Mar-07 4:08
MemberMartin Gagne26-Mar-07 4:08 
GeneralRe: Animation stops while long process executes Pin
jwhite046126-Mar-07 5:24
Memberjwhite046126-Mar-07 5:24 
GeneralRe: Animation stops while long process executes [modified] Pin
Martin Gagne26-Mar-07 5:33
MemberMartin Gagne26-Mar-07 5:33 
GeneralRe: Animation stops while long process executes Pin
jwhite046126-Mar-07 6:59
Memberjwhite046126-Mar-07 6:59 
GeneralRe: Animation stops while long process executes Pin
esupport17-Apr-07 7:21
Memberesupport17-Apr-07 7:21 
GeneralRe: Animation stops while long process executes Pin
SalizarMarxx23-Dec-07 18:31
MemberSalizarMarxx23-Dec-07 18:31 
This is technically incorrect...
There is a simple test an an even easier solution.
Create a Windows Form objcet, add your Loading CIrcle.
Now create a Async Call Method Group.
<br />
delegate void DoSomethingDelegate();<br />
DoSometihngDelegate iDoSomething;<br />
<br />
-- On Load Event<br />
OnLoad()<br />
{<br /> = true;<br />
LoadingCircle1.Visible = true;<br />
idoSomething = new DoSOmethingDelegate(WorkerMethod);<br />
idoSomething.BeginInvoke(DoSomethinCallBack, this);<br />
}<br />
<br />
private void WorkerMethod()<br />
{<br />
 int waitfor = 1000;<br />
for(int i = 0; i < waitfor; i++)<br />
Thread.Sleep(100);<br />
}<br />
<br />
private void DoSometingCallBack(IAsyncResult ar)<br />
{<br />
iDoSomething.EndInvoke(ar);<br />
this.Invoke(new UpdateUIDelegate(UpdateUI));<br />
}<br />
<br />
delegate void UpdateUIDelegate();<br />
private void UpdateUI()<br />
{<br />
//End With UI update<br />
}<br />

The Above Code Works as expected, and there are no issues...
However if you make a slight modification to the Async call stack by using a AsynWaitHandle teh loading circle refuses to animate.
This shouldn't be an issue as even with using the WaitHandle the work is still being done on a second thread away from the UI thread.

The Solution is simple though.
Simply change the time object from a Windows.Forms.Timer to a System.Timer.Timer object which is capable of truly handling mutiple thread events with out issues...

Here the is the code that will not animate correctly with the Form TImer
<br />
void OnLoad<br />
{<br />
iDoSomething = new iDoSOmethingDelegate(WorkerMethod);<br />
IAsyncResult aResult = iDoSomething.BeginInvoke(null, null);<br />
aResult.AsyncWaitHandle.WaitOne();<br />
<br />
iDoSomething.EndInvoke(aResult);<br />
}<br />

GeneralJava Port Pin
gyftakis6-Mar-07 2:46
Membergyftakis6-Mar-07 2:46 
GeneralRe: Java Port Pin
Martin Gagne6-Mar-07 3:18
MemberMartin Gagne6-Mar-07 3:18 
GeneralRe: Java Port Pin
gyftakis6-Mar-07 4:36
Membergyftakis6-Mar-07 4:36 
GeneralRe: Java Port Pin
gyftakis6-Mar-07 7:42
Membergyftakis6-Mar-07 7:42 
GeneralRe: Java Port Pin
Martin Gagne6-Mar-07 7:55
MemberMartin Gagne6-Mar-07 7:55 
GeneralA similar Control Pin
PITRep15-Feb-07 6:06
MemberPITRep15-Feb-07 6:06 
GeneralSpokes Pin
Lukasz Swiatkowski13-Feb-07 6:47
MemberLukasz Swiatkowski13-Feb-07 6:47 
GeneralRe: Spokes Pin
eclipse2k113-Feb-07 23:46
Membereclipse2k113-Feb-07 23:46 
GeneralSupport transparency Pin
Ajek13-Feb-07 3:27
MemberAjek13-Feb-07 3:27 
GeneralRe: Support transparency Pin
Patrick Etc.15-Feb-07 21:34
MemberPatrick Etc.15-Feb-07 21:34 
GeneralSlick, useful, and well written - I vote 5 as well Pin
BradOsterloo12-Feb-07 8:51
MemberBradOsterloo12-Feb-07 8:51 
GeneralRe: Slick, useful, and well written - I vote 5 as well Pin
eclipse2k113-Feb-07 8:45
Membereclipse2k113-Feb-07 8:45 
GeneralAnother addition to the control Pin
Patrick Etc.6-Feb-07 17:33
MemberPatrick Etc.6-Feb-07 17:33 
GeneralRe: Another addition to the control Pin
Martin Gagne6-Feb-07 17:50
MemberMartin Gagne6-Feb-07 17:50 
GeneralRe: Another addition to the control Pin
Patrick Etc.6-Feb-07 18:32
MemberPatrick Etc.6-Feb-07 18:32 
GeneralCoolest. Control. EVER. Pin
Patrick Etc.6-Feb-07 11:08
MemberPatrick Etc.6-Feb-07 11:08 
GeneralRe: Coolest. Control. EVER. Pin
Martin Gagne6-Feb-07 11:28
MemberMartin Gagne6-Feb-07 11:28 

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