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Posted 17 Jul 2006

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A new kind of progress bar for .NET 2.0.

## Introduction

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.

C#
```private PointF GetCoordinate(PointF _objCircleCenter,
{
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.

C#
```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.

## Conclusion

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.

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 Not disposing all GDI+ resources: System.AccessViolationException bwaide22-Apr-08 20:52 bwaide 22-Apr-08 20:52
 Re: Not disposing all GDI+ resources: System.AccessViolationException Martin Gagne23-Apr-08 4:42 Martin Gagne 23-Apr-08 4:42
 Re: Not disposing all GDI+ resources: System.AccessViolationException Luc Pattyn27-Mar-10 22:18 Luc Pattyn 27-Mar-10 22:18
 How to put a Loading Circle in a datgridviewcolmun/cell ? platinum0731-Dec-07 0:08 platinum07 31-Dec-07 0:08
 Re: How to put a Loading Circle in a datgridviewcolmun/cell ? Martin Gagne31-Dec-07 4:03 Martin Gagne 31-Dec-07 4:03
 Re: How to put a Loading Circle in a datgridviewcolmun/cell ? platinum071-Jan-08 9:28 platinum07 1-Jan-08 9:28
 Re: How to put a Loading Circle in a datgridviewcolmun/cell ? Patrick Etc.30-May-08 11:47 Patrick Etc. 30-May-08 11:47
 Windows.Forms.TImer needs to be changed to System.Timers.Timer SalizarMarxx23-Dec-07 18:42 SalizarMarxx 23-Dec-07 18:42
 I ran into an issue with this control in conjunction with an Async WaitHandle The control refused to animate while waiting for the WaitHandle to return. This seemed odd since another loading circle control didn't behave in this manor. I investigated the differences between the two and determined that the other loading indicator was using System.Timers object. I made a quick change to the code and this loading circle started to perform as expected. Heres an example use of the AsyncWaitHandle The Following Code assumes a windows form object with an added Loading Circle control. Copy Code ```
delegate void DoSomethingDelegate();
DoSometihngDelegate iDoSomething;

{
iDoSomething = new iDoSOmethingDelegate(WorkerMethod);
IAsyncResult aResult = iDoSomething.BeginInvoke(null, null);
aResult.AsyncWaitHandle.WaitOne();

iDoSomething.EndInvoke(aResult);
}

private void WorkerMethod()
{
int waitfor = 1000;
for(int i = 0; i < waitfor; i++)
}
```
 How to add this circle control to my toolbox component? CSharp200526-Nov-07 5:35 CSharp2005 26-Nov-07 5:35
 Bug report cacerzard4-Sep-07 23:12 cacerzard 4-Sep-07 23:12
 Re: Bug report Martin Gagne5-Sep-07 4:20 Martin Gagne 5-Sep-07 4:20
 Re: Bug report Luc Pattyn27-Mar-10 22:21 Luc Pattyn 27-Mar-10 22:21
 How can use this control in Visual Basic 6 sixtoja9-Aug-07 8:04 sixtoja 9-Aug-07 8:04
 Re: How can use this control in Visual Basic 6 Martin Gagne9-Aug-07 8:46 Martin Gagne 9-Aug-07 8:46
 Re: How can use this control in Visual Basic 6 sixtoja9-Aug-07 9:36 sixtoja 9-Aug-07 9:36