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Automatic Application Wait Cursor

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16 Mar 2005Public Domain5 min read 362.4K   3.3K   90   77
Use this library to very easily add an application wide WaitCursor whenever your application is working.

Sample Screen Shot from Demo

Introduction

Making your WinForm applications User Friendly is important. One aspect of a good user experience is informing your user that your application is unresponsive during short periods of work. This article introduces an effective and simple way of adding application wide WaitCursors using one line of start-up code.

Background

Recently, I have been working on a WinForms project at home that occasionally performs some short (less than 5 seconds) running tasks. I wanted the user to be informed that during that short period the UI is unresponsive, so I chose to use the Cursors.WaitCursor to indicate this. This article shows how I came to my final WaitCursor library implementation which I believe is a completely re-usable library.

Using the code

From a developer's point of view, using the WaitCursor library could not get any simpler. Add a reference to the WaitCursor assembly and then add the following line to your application start-up code:

C#
ApplicationWaitCursor.Cursor = Cursors.WaitCursor;

That’s it!

You can of course use any Cursor you like, you can use one of the predefined Cursors or you can create a new cursor and use that instead. You can also fine tune the amount of work time that will elapse before the Cursor is shown:

C#
ApplicationWaitCursor.Delay = 
             new TimeSpan(0, 0, 0, 1, 0);  // Delay of 1 second

How the library came about

During development of a recent WinForms project at home, I had decided to use the cursor to indicate short running tasks to the user, like so:

C#
private void DoShortRunningTask()
{
    Cursor.Current = Cursors.WaitCursor; 

    .. do some work .. 

    Cursor.Current = Cursors.Default; 
}

Now, before you say "Where’s the exception handling code?", I am trying to illustrate how I eventually came to my final cut of the WaitCursor library.

The above code works, or, at least it works most of the time. I, of course, found that without any exception handling I could end up with the WaitCursor on permanently, so I quickly came up with:

private void DoShortRunningTask()
{
  Cursor.Current = Cursors.WaitCursor;
  try
  {
    .. do some work ..
  }
  finally
  {
    Cursor.Current = Cursors.Default;
  }
}

Now that’s better, I've guaranteed that the Cursor will always be returned to the Default cursor even if an exception occurs. However, I found it arduous to wrap that code around every short running task that I was developing.

Then I remembered how I used to use C++ stack based destructors to perform tear down work upon exiting of a method:

void DoShortRunningTask()
{
StWaitCursor cursor = new StWaitCursor();

  .. do some work .. 
// Implicitly called ~StWaitCursor returns the Cursor to Default


}

But I couldn't use C# destructors the same way since you can't guarantee when a C# destructor is called since the Garbage Collector thread is responsible for that.

Instead, C# uses a different language feature, the using statement which implicitly calls the Dispose method of objects that implement IDisposable. Although (I find it's) not quite as easy to use as the C++ destructor, you can achieve the same result with the using statement:

C#
private void DoShortRunningTask()
{
    using (new StWaitCursor())
    { 
        .. do some work .. 
    } 
}

This code, of course, requires the StWaitCursor class:

C#
public class StWaitCursor : IDisposable
{
  public StWaitCursor()
  {
    Cursor.Current = Cursors.WaitCursor;
  }
  public void Dispose()
  {
    Cursor.Current = Cursors.Default;
  }
}

There, nice and simple. I found, however, that if my short running task was too short then the user sees a quick flickering of the Cursor to and from the WaitCursor, quite annoying. So I decided I needed a way of turning the WaitCursor on after a predefined amount of time during a task.

After quite a few iterations and refactorings, I came up with what I called the StDelayedCallback class (see source code) which is a generic class that once instantiated will wait for a specified amount of time before calling the Start method of an IDelayedCallbackHandler, and if Start was called that it was guaranteed to call the Finish method of the same interface. Once I had this, I could easily implement the interface such that the WaitCursor was turned on when Start was called and returned the Default cursor when Finish was called.

Some things I found

During development of the WaitCursor library, I discovered that I could not set Cursor.Current on any thread other than the GUI thread. This is where the Win32 AttachThreadInput method can be used to get around this problem effectively. So I developed the StThreadAttachedDelayedCallback class which wraps up the call to the AttachThreadInput.

So eventually I ended up with a generic StDelayedCallback class, a ThreadInput attached version of it called StThreadAttachedDelayedCallback and a specific Cursor implementation called StWaitCursor. Incidentally, I used the prefix St since I had originally intended on using these classes in a similar way to the C++ Stack based classes I had used in the past. So up until now, I had intended on using the following:

C#
private void DoShortRunningTask()
{
  using (new StWaitCursor(new TimeSpan(0, 0, 0, 0, 500))
  {
    .. do some work ..
  }
}

However, it still meant I had to be explicit about where I wanted my WaitCursor to show.

Then I had an attack of brilliance and came up with the ApplicationWaitCursor singleton class which neatly wraps the StWaitCursor such that whenever the application is working, or rather, whenever it’s not regularly calling OnApplicationIdle, then the StWaitCursor kicks in and shows the WaitCursor.

The only caveat I found was when I dragged a window around which blocks the OnApplicationIdle call. So, I also intercept the WM_NCLBUTTONDOWN message (which is sent at the beginning of the window dragging) to temporarily disable the StWaitCursor.

That's where I am up to with the current WaitCursor implementation and in brief how I got there. You can easily derive from the StDelayedCallback class to create similar effects. Perhaps you would like to show an Indefinite progress bar during your long running tasks, or indicate "Saving Changes..." in a StatusBar control:

C#
private void SaveChanges()
{
  using (new StStatusBar(stbMain, "Saving Changes...")
  {
    .. do some work ..
  }
  // StStatusBar.IDispose could return the Text
  // of the StatusBar to its original value 
}

Note that the source code does not contain the StStatusBar class, I am just using it as an example of other ways you could use the StDelayedCallback class.

History

Version 1.0.0.0 (12th March 2005)

  • Initial version.

Version 1.0.1.0 (16th March 2005)

  • Updated to be CLS compliant (thanks to C a r l and Mathew Hall for pointing this out).

License

This article, along with any associated source code and files, is licensed under A Public Domain dedication


Written By
Web Developer
Australia Australia
I am a .NET Developer living in Melbourne, Australia. I am happily married with 2 gorgeous little girls, Georgia and Maddison.

Comments and Discussions

 
GeneralMy vote of 4 Pin
Rafique Sheikh18-Mar-13 14:52
Rafique Sheikh18-Mar-13 14:52 
GeneralMy vote of 5 Pin
foxaxel17-Nov-11 0:39
foxaxel17-Nov-11 0:39 
QuestionThank you, a small issue we are noticing Pin
reddyp8213-Oct-11 12:14
reddyp8213-Oct-11 12:14 
GeneralAny solutions to the problems below Pin
Matthew Goldman21-Feb-11 4:21
Matthew Goldman21-Feb-11 4:21 
GeneralMy vote of 5 Pin
crocher6-Feb-11 15:08
crocher6-Feb-11 15:08 
GeneralGood job Pin
BillW3322-Oct-10 6:46
professionalBillW3322-Oct-10 6:46 
GeneralNice article Pin
dan!sh 14-Jun-10 6:23
professional dan!sh 14-Jun-10 6:23 
GeneralCursors goes to wait cursor in windows Copy paste menu dialog Pin
erikgenwise18-Feb-10 2:15
erikgenwise18-Feb-10 2:15 
GeneralRe: Cursors goes to wait cursor in windows Copy paste menu dialog Pin
Matthew Goldman4-Feb-11 11:43
Matthew Goldman4-Feb-11 11:43 
GeneralNice Job !! Pin
Borun8-Jun-09 8:08
Borun8-Jun-09 8:08 
GeneralA Few More Bugs Pin
chewmon3420-Mar-09 5:54
chewmon3420-Mar-09 5:54 
GeneralWorks... mostly Pin
Jakub Janda4-Mar-09 1:10
Jakub Janda4-Mar-09 1:10 
GeneralStill brilliant after 3 years! Pin
seankearon5-Feb-09 12:21
seankearon5-Feb-09 12:21 
GeneralBrilliant, thanks a lot! Pin
Heribert117-Oct-08 0:21
Heribert117-Oct-08 0:21 
GeneralIs it possible to use this in a VS2008 C++ Windows Forms application Pin
bencbr16-Sep-08 8:52
bencbr16-Sep-08 8:52 
GeneralRe: Is it possible to use this in a VS2008 C++ Windows Forms application Pin
Steve Fillingham19-Sep-08 1:08
Steve Fillingham19-Sep-08 1:08 
QuestionRe: Is it possible to use this in a VS2008 C++ Windows Forms application Pin
TheBerk9-Jan-09 10:29
TheBerk9-Jan-09 10:29 
AnswerRe: Is it possible to use this in a VS2008 C++ Windows Forms application Pin
HowitZer2623-Feb-09 11:08
HowitZer2623-Feb-09 11:08 
First download the source and then build it in C# to create the dll. This dll can be used in a C++ Forms application. Add a reference to your C++ project and select the WaitCursor.dll.

The using statement for c++ is "using namespace ConceptCave::WaitCursor;"
QuestionCan this work with WPF Pin
sreeni7320-Jul-08 10:10
sreeni7320-Jul-08 10:10 
GeneralWait cursor shows when holding mouse button down on a scroll bar Pin
QStarin9-Jul-08 7:03
QStarin9-Jul-08 7:03 
GeneralRe: Wait cursor shows when holding mouse button down on a scroll bar Pin
gezanal16-Dec-08 7:58
gezanal16-Dec-08 7:58 
QuestionWhat version of the .NET Framework has this been tested on? Pin
Matt Christenson28-May-08 6:09
Matt Christenson28-May-08 6:09 
AnswerRe: What version of the .NET Framework has this been tested on? Pin
QStarin9-Jul-08 6:50
QStarin9-Jul-08 6:50 
GeneralRe: What version of the .NET Framework has this been tested on? Pin
Steve Fillingham11-Jul-08 15:44
Steve Fillingham11-Jul-08 15:44 
Generalvery good. Pin
ali_reza_zareian17-Apr-08 0:43
ali_reza_zareian17-Apr-08 0:43 

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