LEADTOOLS (Leadtools assembly)
LEAD Technologies, Inc

Disposed Event

Example 





Leadtools Namespace > RasterImage Class : Disposed Event
Occurs when the image is disposed by a call to the Dispose method. .NET support Silverlight support
Syntax
public event EventHandler<EventArgs> Disposed
'Declaration
 
Public Event Disposed As EventHandler(Of EventArgs)
'Usage
 
Dim instance As RasterImage
Dim handler As EventHandler(Of EventArgs)
 
AddHandler instance.Disposed, handler
public event EventHandler<~Remove~> Disposed
add_Disposed(function(sender, e))
remove_Disposed(function(sender, e))


public:
event EventHandler<EventArgs^>^ Disposed
Remarks

When you create a Disposed delegate, you identify the method that handles the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate.

The Disposed event will fire whenever the Dispose method of this object is called. After this event occurs, the RasterImage object is disposed and should not be used anymore. It is recommended that you remove the handler to the Dispose event so the .NET Garbage Collector runtime can remove the object from its internal use and mark it as "unused".

If the RasterImage is being freed as a result of the .NET Garbage Collector, in other worlds, the object finalizer is being called, then this event will not occur.

Example
  
Private Sub DisposedEventExample()
      ' Startup
      Dim codecs As New RasterCodecs()
      ' Load an image
      Dim image1 As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp"))

      ' Add a handler to the Disposed event
      Console.WriteLine("Adding handler to Disposed for image with format " + image1.OriginalFormat.ToString())
      AddHandler image1.Disposed, AddressOf rasterImage_Disposed

      ' Now dispose the image
      Console.WriteLine("Calling .Dispose to image with format " + image1.OriginalFormat.ToString())
      image1.Dispose()

      ' Now use the "using" syntax
      Using image2 As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "cannon.jpg"))
         ' Add a handler to the Disposed event
         Console.WriteLine("Adding handler to Disposed for image with format " + image2.OriginalFormat.ToString())
         AddHandler image2.Disposed, AddressOf rasterImage_Disposed

         ' The event should occur at the next line
         Console.WriteLine("Will be disposed after this, format " + image2.OriginalFormat.ToString())
      End Using

      ' Load another image
      Dim image3 As RasterImage = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir, "Ocr1.tif"))

      ' Add a handler to the Disposed event
      Console.WriteLine("Adding handler to Disposed for image with format " + image3.OriginalFormat.ToString())
      AddHandler image3.Disposed, AddressOf rasterImage_Disposed

      ' Do not dispose the image
      Console.WriteLine("Never disposing image with format " + image3.OriginalFormat.ToString())

      ' Notice that the event will never occur for image3. The image is not going to be disposed
      ' only its finalizer called. The garbage collector cannot guarantee that our event handler
      ' is still a valid object. This scenario creates resource leaks and it is recommended that
      ' you always dispose and object that implements the IDisposable interface, like we did
      ' with image1 and image2

      codecs.Dispose()
   End Sub

   Private Sub rasterImage_Disposed(ByVal sender As Object, ByVal e As EventArgs)
      ' Get the RasterImage object being disposed
      Dim image As RasterImage = DirectCast(sender, RasterImage)
      Console.WriteLine("Being disposed, image with format " + image.OriginalFormat.ToString())

      ' Remove the handler to decouple the object from our application
      ' and let the garbage collector take over
      RemoveHandler image.Disposed, AddressOf rasterImage_Disposed
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class
private void DisposedEventExample()
   {
      // Startup
      RasterCodecs codecs = new RasterCodecs();
      // Load an image
      RasterImage image1 = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir,"Image1.cmp"));

      // Add a handler to the Disposed event
      Console.WriteLine("Adding handler to Disposed for image with format " + image1.OriginalFormat);
      image1.Disposed += new EventHandler<EventArgs>(rasterImage_Disposed);

      // Now dispose the image
      Console.WriteLine("Calling .Dispose to image with format " + image1.OriginalFormat);
      image1.Dispose();

      // Now use the "using" syntax
      using(RasterImage image2 = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir,"Master.jpg")))
      {
         // Add a handler to the Disposed event
         Console.WriteLine("Adding handler to Disposed for image with format " + image2.OriginalFormat);
         image2.Disposed += new EventHandler<EventArgs>(rasterImage_Disposed);

         // The event should occur at the next line
         Console.WriteLine("Will be disposed after this, format " + image2.OriginalFormat);
      }

      // Load another image
      RasterImage image3 = codecs.Load(Path.Combine(LEAD_VARS.ImagesDir,"Ocr1.tif"));

      // Add a handler to the Disposed event
      Console.WriteLine("Adding handler to Disposed for image with format " + image3.OriginalFormat);
      image3.Disposed += new EventHandler<EventArgs>(rasterImage_Disposed);

      // Do not dispose the image
      Console.WriteLine("Never disposing image with format " + image3.OriginalFormat);

      // Notice that the event will never occur for image3. The image is not going to be disposed
      // only its finalizer called. The garbage collector cannot guarantee that our event handler
      // is still a valid object. This scenario creates resource leaks and it is recommended that
      // you always dispose and object that implements the IDisposable interface, like we did
      // with image1 and image2

      codecs.Dispose();
   }

   private void rasterImage_Disposed(object sender, EventArgs e)
   {
      // Get the RasterImage object being disposed
      RasterImage image = sender as RasterImage;
      Console.WriteLine("Being disposed, image with format " + image.OriginalFormat);

      // Remove the handler to decouple the object from our application
      // and let the garbage collector take over
      image.Disposed -= new EventHandler<EventArgs>(rasterImage_Disposed);
   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}
public void DisposedEventExample()
{
   // Create an image
   RasterImage image1 = new RasterImage(RasterMemoryFlags.Conventional, 100, 100, 24, RasterByteOrder.Bgr, RasterViewPerspective.TopLeft, null, null, 0);
   // Add a handler to the Disposed event
   Debug.WriteLine("Adding handler to Disposed for image with format " + image1.OriginalFormat);
   image1.Disposed += new EventHandler<EventArgs>(rasterImage_Disposed);

   // Now dispose the image
   Debug.WriteLine("Calling .Dispose to image with format " + image1.OriginalFormat);
   image1.Dispose();

   // Now use the "using" syntax
   using (RasterImage image2 = new RasterImage(RasterMemoryFlags.Conventional, 100, 100, 24, RasterByteOrder.Bgr, RasterViewPerspective.TopLeft, null, null, 0))
   {
      // Add a handler to the Disposed event
      Debug.WriteLine("Adding handler to Disposed for image with format " + image2.OriginalFormat);
      image2.Disposed += new EventHandler<EventArgs>(rasterImage_Disposed);

      // The event should occur at the next line
      Debug.WriteLine("Will be disposed after this, format " + image2.OriginalFormat);
   }

   // Load another image
   RasterImage image3 = new RasterImage(RasterMemoryFlags.Conventional, 100, 100, 24, RasterByteOrder.Bgr, RasterViewPerspective.TopLeft, null, null, 0);

   // Add a handler to the Disposed event
   Debug.WriteLine("Adding handler to Disposed for image with format " + image3.OriginalFormat);
   image3.Disposed += new EventHandler<EventArgs>(rasterImage_Disposed);

   // Do not dispose the image
   Debug.WriteLine("Never disposing image with format " + image3.OriginalFormat);

   // Notice that the event will never occur for image3. The image is not going to be disposed
   // only its finalizer called. The garbage collector cannot guarantee that our event handler
   // is still a valid object. This scenario creates resource leaks and it is recommended that
   // you always dispose and object that implements the IDisposable interface, like we did
   // with image1 and image2
}

private void rasterImage_Disposed(object sender, EventArgs e)
{
   // Get the RasterImage object being disposed
   RasterImage image = sender as RasterImage;
   Debug.WriteLine("Being disposed, image with format " + image.OriginalFormat);

   // Remove the handler to decouple the object from our application
   // and let the garbage collector take over
   image.Disposed -= new EventHandler<EventArgs>(rasterImage_Disposed);
}
Public Sub DisposedEventExample()
   ' Create an image
   Dim image1 As RasterImage = New RasterImage(RasterMemoryFlags.Conventional, 100, 100, 24, RasterByteOrder.Bgr, RasterViewPerspective.TopLeft, Nothing, Nothing, 0)
   ' Add a handler to the Disposed event
   Debug.WriteLine("Adding handler to Disposed for image with format " & image1.OriginalFormat)
   AddHandler image1.Disposed, AddressOf rasterImage_Disposed

   ' Now dispose the image
   Debug.WriteLine("Calling .Dispose to image with format " & image1.OriginalFormat)
   image1.Dispose()

   ' Now use the "using" syntax
   Using image2 As RasterImage = New RasterImage(RasterMemoryFlags.Conventional, 100, 100, 24, RasterByteOrder.Bgr, RasterViewPerspective.TopLeft, Nothing, Nothing, 0)
      ' Add a handler to the Disposed event
      Debug.WriteLine("Adding handler to Disposed for image with format " & image2.OriginalFormat)
      AddHandler image2.Disposed, AddressOf rasterImage_Disposed

      ' The event should occur at the next line
      Debug.WriteLine("Will be disposed after this, format " & image2.OriginalFormat)
   End Using

   ' Load another image
   Dim image3 As RasterImage = New RasterImage(RasterMemoryFlags.Conventional, 100, 100, 24, RasterByteOrder.Bgr, RasterViewPerspective.TopLeft, Nothing, Nothing, 0)

   ' Add a handler to the Disposed event
   Debug.WriteLine("Adding handler to Disposed for image with format " & image3.OriginalFormat)
   AddHandler image3.Disposed, AddressOf rasterImage_Disposed

   ' Do not dispose the image
   Debug.WriteLine("Never disposing image with format " & image3.OriginalFormat)

   ' Notice that the event will never occur for image3. The image is not going to be disposed
   ' only its finalizer called. The garbage collector cannot guarantee that our event handler
   ' is still a valid object. This scenario creates resource leaks and it is recommended that
   ' you always dispose and object that implements the IDisposable interface, like we did
   ' with image1 and image2
End Sub

Private Sub rasterImage_Disposed(ByVal sender As Object, ByVal e As EventArgs)
   ' Get the RasterImage object being disposed
   Dim image As RasterImage = TryCast(sender, RasterImage)
   Debug.WriteLine("Being disposed, image with format " & image.OriginalFormat)

   ' Remove the handler to decouple the object from our application
   ' and let the garbage collector take over
   RemoveHandler image.Disposed, AddressOf rasterImage_Disposed
End Sub
Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

See Also

Reference

RasterImage Class
RasterImage Members

 

 

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