public event ExportEndEventHandler ExportEnd

Public Event ExportEnd As ExportEndEventHandler

void reportViewer1_ExportEnd(object sender, Telerik.ReportViewer.Common.ExportEndEventArgs args)
{
    if (null != args.Exception)
    {
        //some logic if report processing is not successful
    }
    else
    {
        //suppress the viewer SaveFileDialog and use your own
        args.Handled = true;
        var fileName = args.DocumentName;
        var extension = args.DocumentExtension;
        var filter = string.Format("{0} (*.{1})|*.{1}|All Files (*.*)|*.*",
                                    fileName,
                                    extension);

        var saveFileDlg = new SaveFileDialog
        {
            Filter = filter,
            FileName = fileName + "." + extension,
        };

        if (saveFileDlg.ShowDialog() == DialogResult.OK)
        {
            try
            {
                using (var fs = new FileStream(saveFileDlg.FileName, FileMode.Create))
                {
                    fs.Write(args.DocumentBytes, 0, args.DocumentBytes.Length);
                }

                //Optionally open the file
                if (!string.IsNullOrEmpty(saveFileDlg.FileName))
                {
                    System.Diagnostics.Process.Start(saveFileDlg.FileName);
                }
            }
            catch (Exception)
            {
                //Handle exception
            }
        }
    }
}

Private Sub reportViewer1_ExportEnd(sender As Object, args As Telerik.ReportViewer.Common.ExportEndEventArgs)
    'some logic if report processing is not successful
    If args.Exception IsNot Nothing Then
    Else
        'suppress the viewer SaveFileDialog and use your own
        args.Handled = True
        Dim fileName = args.DocumentName
        Dim extension = args.DocumentExtension
        Dim filter = String.Format("{0} (*.{1})|*.{1}|All Files (*.*)|*.*", fileName, extension)

        Dim saveFileDlg = New SaveFileDialog() With { _
            .Filter = filter, _
            .FileName = fileName + "." + extension _
        }

        If saveFileDlg.ShowDialog() = DialogResult.OK Then
            Try
                Using fs = New FileStream(saveFileDlg.FileName, FileMode.Create)
                    fs.Write(args.DocumentBytes, 0, args.DocumentBytes.Length)
                End Using

                'Optionally open the file
                If Not String.IsNullOrEmpty(saveFileDlg.FileName) Then
                    System.Diagnostics.Process.Start(saveFileDlg.FileName)
                End If
                'Handle exception
            Catch generatedExceptionName As Exception
            End Try
        End If
    End If
End Sub