CancelAsync Method

Visual Basic
C#
WinRT C#
WinRT JavaScript
C++

public void CancelAsync()

'Declaration
 
Public Sub CancelAsync()

'Usage
 
Dim instance As RasterCodecs
 
instance.CancelAsync()

public void CancelAsync()

 function Leadtools.Codecs.RasterCodecs.CancelAsync()

public:
void CancelAsync();

The RasterCodecs object supports getting information and loading image files asynchronously through the use of the GetInformationAsync(String,Boolean,Int32,Object) and LoadAsync(String,LeadRect,Int32,CodecsLoadByteOrder,Int32,Int32,Object) methods.

You can call one asynchronous operation per RasterCodecs object at a time. To determine whether the RasterCodecs object is busy with a previous asynchronous operation, use IsAsyncBusy property. This is the equivalent of the WebClient.IsBusy property of AsyncWebClient.

You can also use the CancelAsync method to cancel any current asynchronous operation in this RasterCodecs object. This is the equivalent of calling WebClient.CancelAsync on AsyncWebClient.

Note:UseAsync, AsyncWebClient, IsAsyncBusy, and CancelAsync are only applicable when the GetInformationAsync(String,Boolean,Int32,Object) or LoadAsync(String,LeadRect,Int32,CodecsLoadByteOrder,Int32,Int32,Object) was with the versions that take a System.Uri parameter. The versions that take a System.String or a System.IO.Stream does not use a System.Net.WebClient object internally. If you want to check the progress or cancel the operation then use the LoadImage event as normal.

Visual Basic
C#
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Public Sub CancelAsyncExample()
      Dim srcFileName As String = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp")
      Dim uri As New Uri(srcFileName)

      Dim codecs As New RasterCodecs()

      ' Now Load the file asynchronously
      AddHandler codecs.LoadAsyncCompleted, AddressOf cancelAsyncExample_LoadAsyncCompleted
      Dim image As RasterImage = codecs.LoadAsync(uri, Nothing)

      ' Cancel it immediatly, in normal situation, the cancelation will happen
      ' before the LoadAsync method has a chance to load the file and
      ' the message "User canceled" will be displayed on the console
      If codecs.IsAsyncBusy Then
         codecs.CancelAsync()
      End If
   End Sub

   Private Sub cancelAsyncExample_LoadAsyncCompleted(ByVal sender As Object, ByVal e As CodecsLoadAsyncCompletedEventArgs)
      If e.Cancelled Then
         Console.WriteLine("User canceled")
      ElseIf Not IsNothing(e.Error) Then
         Console.WriteLine("Error: " + e.Error.Message)
      Else
         ' Get the image
         Dim image As RasterImage = e.Image
         Console.WriteLine("Image loaded asynchronously: Size = {0} by {1}", image.Width, image.Height)
         image.Dispose()
      End If

      ' Unsubscribe to the event and dispose the RasterCodecs object
      Dim codecs As RasterCodecs = DirectCast(sender, RasterCodecs)
      RemoveHandler codecs.LoadAsyncCompleted, AddressOf cancelAsyncExample_LoadAsyncCompleted
      codecs.Dispose()
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class

public void CancelAsyncExample()
     {
         string srcFileName = Path.Combine(LEAD_VARS.ImagesDir, "Image1.cmp");
         Uri uri = new Uri(srcFileName);

         RasterCodecs codecs = new RasterCodecs();

         // Now Load the file asynchronously
         codecs.LoadAsyncCompleted += new EventHandler<CodecsLoadAsyncCompletedEventArgs>(cancelAsyncExample_LoadAsyncCompleted);
         RasterImage image = codecs.LoadAsync(uri, null);

         // Cancel it immediatly, in normal situation, the cancelation will happen
         // before the LoadAsync method has a chance to load the file and
         // the message "User canceled" will be displayed on the console
         if (codecs.IsAsyncBusy)
         {
             codecs.CancelAsync();
         }
     }

     private void cancelAsyncExample_LoadAsyncCompleted(object sender, CodecsLoadAsyncCompletedEventArgs e)
     {
         if (e.Cancelled)
         {
             Console.WriteLine("User canceled");
         }
         else if (e.Error != null)
         {
             Console.WriteLine("Error: " + e.Error.Message);
         }
         else
         {
             // Get the image
             RasterImage image = e.Image;
             Console.WriteLine("Image loaded asynchronously: Size = {0} by {1}", image.Width, image.Height);
             image.Dispose();
         }

         // Unsubscribe to the event and dispose the RasterCodecs object
         RasterCodecs codecs = sender as RasterCodecs;
         codecs.LoadAsyncCompleted -= new EventHandler<CodecsLoadAsyncCompletedEventArgs>(cancelAsyncExample_LoadAsyncCompleted);
         codecs.Dispose();
     }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

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

Reference

RasterCodecs Class
RasterCodecs Members