Form1.vb

Imports System
Imports System.Threading
Imports System.Windows.Forms
Imports DevExpress.Spreadsheet

Namespace WorkbookProgressSample

    Public Partial Class Form1
        Inherits Form

        Private cancellationSource As CancellationTokenSource

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Async Sub RunCancel_Click(ByVal sender As Object, ByVal e As EventArgs)
            If cancellationSource IsNot Nothing Then
                cancellationSource.Cancel()
            Else
                progressBarLoad.Value = 0
                progressBarExport.Value = 0
                btnRunCancel.Text = "Cancel"
                cancellationSource = New CancellationTokenSource()
                Try
                    Using workbook As Workbook = New Workbook()
                        Await workbook.LoadDocumentAsync("Document.xlsx", cancellationSource.Token, New Progress(Of Integer)(Sub(progress)
                            progressBarLoad.Value = progress
                            progressBarLoad.Refresh()
                        End Sub))
                        Await workbook.ExportToPdfAsync("Result.pdf", cancellationSource.Token, New Progress(Of Integer)(Sub(progress)
                            progressBarExport.Value = progress
                            progressBarExport.Refresh()
                        End Sub))
                    End Using
                Catch __unusedOperationCanceledException1__ As OperationCanceledException
                    progressBarLoad.Value = 0
                    progressBarExport.Value = 0
                Finally
                    cancellationSource.Dispose()
                    cancellationSource = Nothing
                    btnRunCancel.Text = "Run"
                End Try
            End If
        End Sub

        Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As FormClosingEventArgs)
            cancellationSource?.Cancel()
        End Sub
    End Class
End Namespace