CancelAsync Method

C#
Visual Basic
WinRT C#
Objective-C
Java
WinRT JavaScript
C++

public void CancelAsync()

'Declaration
 
Public Sub CancelAsync()

'Usage
 
Dim instance As RasterCodecs
 
instance.CancelAsync()

public void CancelAsync()

public void cancelAsync(Object operation)

 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.

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

Copy Code

Imports Leadtools
Imports Leadtools.Codecs
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color
Imports Leadtools.Drawing

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

using Leadtools;
using Leadtools.Codecs;
using Leadtools.ImageProcessing;
using Leadtools.ImageProcessing.Color;

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

Reference

RasterCodecs Class
RasterCodecs Members