ActiveReports 16 .NET Edition
ActiveReports 16 User Guide / Export Reports / Managing Asynchronous or Long-Running Report Rendering
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    Managing Asynchronous or Long-Running Report Rendering
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    You can manage asynchronous or long-running report rendering. ActiveReports provides a number of possibilities to control the export process, which can help you create more responsive applications. In this topic, we discuss common use cases of the report rendering:

    Display Progress Information

    Let's see how you can have displayed the export rendering progress information, using a WinForms Viewer application. As an example, we will take the Export sample that you can access at this link - https://github.com/activereports/Samples16/tree/main/API/PageAndRDL/Export.

    The rendering progress information can be displayed for PDF, Image, HTML, and Excel exports at the report rendering.

    Note: The progress information is not shown if the report is exported with the Pagination property set to False (Image, Excel Rendering Extensions) or with the Mode property set to Galley (HTML Rendering Extension).
    1. Open the Export sample project.
    2. From the Visual Studio toolbox, drag the Label control onto the Form.
    3. Add this code into the Form.
      Visual Basic.NET code
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      Private Async Sub ExportAsync(ByVal report As PageReport, ByVal renderingExtension As IRenderingExtension, ByVal outputProvider As StreamProvider, ByVal settings As NameValueCollection)
         labelExport.Text = "Export started..."
         Dim control = Me 
         Dim progress = New Progress(Of ProgressInfo)(Sub(progressInfo)
            control.BeginInvoke(New MethodInvoker(Sub()
               labelExport.Text = If(progressInfo.IsLast = True, "Export is finished." , $"Exported {progressInfo.PageNumber} pages.")
            End Sub))
         End Sub)
         
         await Task.Run(Sub()
            Try
               report.Document.Render(renderingExtension, outputProvider, settings, False, False, CancellationToken.None, progress)
            Catch e as Exception
            End Try
         End Sub)
      End Sub                              
      
      C# code
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      private async void ExportAsync(PageReport report, IRenderingExtension renderingExtension, StreamProvider outputProvider, NameValueCollection settings)
      {
         labelExport.Text = "Export started...";
         var control = this;
         var progress = new Progress(progressInfo =>
         {
            control.BeginInvoke(new MethodInvoker(() =>
            {
               labelExport.Text = progressInfo.IsLast ? "Export is finished." : $"Exported {progressInfo.PageNumber} pages.";
                  
            }));
         });
         await Task.Run(() =>
         {
            try
            {
               report.Document.Render(renderingExtension, outputProvider, settings, false, false, CancellationToken.None, progress);
            }
            catch
            {
               // ignored
            }
         });
      }                                
      
         
    4. Run the project.
    5. In the Export form, select PDF, Image, HTML, or Excel export type.
    6. Click the Export button and see the progress information in the new label.
      Click the Export button in Export Sample Report

    Cancel Report Rendering

    You can cancel the report rendering or export by using the following code.

    Visual Basic.NET code
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    Dim _cancellationTokenSource
    
    Private Async Sub ExportAsync(ByVal report As PageReport, ByVal renderingExtension As IRenderingExtension, ByVal outputProvider As FileStreamProvider, ByVal settings As NameValueCollection)
       _cancellationTokenSource = New CancellationTokenSource()
       exportButton.Text = "Cancel"
       RemoveHandler exportButton.Click, AddressOf exportButton_Click
       AddHandler exportButton.Click, AddressOf CancelExport
       Await Task.Run(Sub()
          Try
             report.Document.Render(renderingExtension, outputProvider, settings, False, False, _cancellationTokenSource.Token)
          Catch unusedOperationCanceledException As OperationCanceledException
          End Try
       End Sub)
       If _cancellationTokenSource.IsCancellationRequested Then MessageBox.Show("Export was cancelled", "Export", MessageBoxButtons.OK, MessageBoxIcon.Information)
       _cancellationTokenSource.Dispose()
       _cancellationTokenSource = Nothing
       RemoveHandler exportButton.Click, AddressOf CancelExport
       AddHandler exportButton.Click, AddressOf exportButton_Click
       exportButton.Text = "Export"
    End Sub
    
    Private Sub CancelExport(ByVal sender As Object, ByVal e As EventArgs)
       _cancellationTokenSource?.Cancel()
    End Sub 
    
    C# code
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    private CancellationTokenSource _cancellationTokenSource;                 
    private async void ExportAsync(PageReport report, IRenderingExtension renderingExtension, FileStreamProvider outputProvider, NameValueCollection settings)
    {
       _cancellationTokenSource = new CancellationTokenSource();
       exportButton.Text = "Cancel";
       exportButton.Click -= exportButton_Click;
       exportButton.Click += cancelExport;
         
       await Task.Run(() =>
       {
          try
          {
             report.Document.Render(renderingExtension, outputProvider, settings, false, false, _cancellationTokenSource.Token);
          }
          catch (OperationCanceledException)
          {
          }
       });
         
       if (_cancellationTokenSource.IsCancellationRequested)
           MessageBox.Show("Export was cancelled", "Export", MessageBoxButtons.OK, MessageBoxIcon.Information);
       _cancellationTokenSource.Dispose();
       _cancellationTokenSource = null;
       exportButton.Click -= cancelExport;
       exportButton.Click += exportButton_Click;
       exportButton.Text = "Export";
    }
         
    private void cancelExport(object sender, EventArgs e)
    {
       _cancellationTokenSource?.Cancel();
    }        
    

    Information Logging

    To log information on the report rendering, add Trace Listeners (see https://docs.microsoft.com/en-us/dotnet/framework/debug-trace-profile/trace-listeners for more information). As an example, modify the ExportAsync function as follows.

    Visual Basic.NET code
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    Private Async Sub ExportAsync(ByVal report As PageReport, ByVal renderingExtension As IRenderingExtension, ByVal outputProvider As StreamProvider, ByVal settings As NameValueCollection)
       labelExport.Text = "Export started..."
       Dim control = Me 
       Dim progress = New Progress(Of ProgressInfo)(Sub(progressInfo)
          control.BeginInvoke(New MethodInvoker(Function()
             labelExport.Text = If(progressInfo.IsLast = True, "Export is finished." , $"Exported {progressInfo.PageNumber} pages.")
             Trace.TraceInformation($"Exported {progressInfo.PageNumber} pages.")
          End Function))
       End Sub)
       await Task.Run(Sub()
          Try
             Dim traceWriter = New TextWriterTraceListener("TextWriterOutput.log", "myListener")
             Trace.Listeners.Clear()
             Trace.Listeners.Add(traceWriter)
             report.Document.Render(renderingExtension, outputProvider, settings, False, False, CancellationToken.None, progress)
             Trace.Flush()
             Trace.Listeners.Clear()
          Catch e as Exception
          End Try
       End Sub)
    End Sub 
    
    C# code
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    private async void ExportAsync(PageReport report, IRenderingExtension renderingExtension, StreamProvider outputProvider, NameValueCollection settings)
    {
       labelExport.Text = "Export started...";
       var control = this;
       var progress = new Progress(progressInfo =>
       {
          control.BeginInvoke(new MethodInvoker(() =>
          {
             labelExport.Text = progressInfo.IsLast ? "Export is finished." : $"Exported {progressInfo.PageNumber} pages.";
             Trace.TraceInformation($"Exported {progressInfo.PageNumber} pages.");
          }));
       });
       await Task.Run(() =>
       {
          try
          {
             var traceWriter = new TextWriterTraceListener("TextWriterOutput.log", "myListener");
             Trace.Listeners.Clear();
             Trace.Listeners.Add(traceWriter);
             report.Document.Render(renderingExtension, outputProvider, settings, false, false, CancellationToken.None, progress);
             Trace.Flush();
             Trace.Listeners.Clear();  
          }
          catch
          {
             // ignored
          }
       });
    }