How can I pause uploading File to Dropbox in .Net

Question

I use VB.Net with .NET Framework 4.6.2 on Windows 10 32bit, my file is almost 12mb.

I use this code to upload files to Dropbox.

Public Async Function ChunkUpload(ByVal ThisFilePath As String, Progress1 As ToolStripProgressBar,
                                      Optional folder As String = ("/Tests")) As Task
        Dim config = New DropboxClientConfig("Project.vb")
        Dim client = New DropboxClient(My.Settings.AccessToken, config)
        Const chunkSize As Integer = 1024 * 1024
        Dim LocalFileName As String = ThisFilePath.Remove(0, ThisFilePath.LastIndexOf("\") + 1)
        Dim fs As IO.FileStream = New IO.FileStream(ThisFilePath, IO.FileMode.Open)
        Dim data As Byte() = New Byte(fs.Length) {}
        fs.Read(data, 0, data.Length)
        fs.Close()
        Try
            Using thisstream = New IO.MemoryStream(data)
                Dim numChunks As Integer = CType(Math.Ceiling((CType(thisstream.Length, Double) / chunkSize)), Integer)
                Dim buffer() As Byte = New Byte((chunkSize) - 1) {}
                Dim sessionId As String = Nothing
                Dim idx = 0
                Do While idx < numChunks
                    Dim byteRead = thisstream.Read(buffer, 0, chunkSize)
                    Dim memStream As IO.MemoryStream = New IO.MemoryStream(buffer, 0, byteRead)
                    If idx = 0 Then
                        Dim result = Await client.Files.UploadSessionStartAsync(body:=memStream)
                        sessionId = result.SessionId
                    Else
                        Dim cursor As Files.UploadSessionCursor = New Files.UploadSessionCursor(sessionId, CType((chunkSize * idx), ULong))
                        If idx = numChunks - 1 Then
                            'Overwrite, if existed
                            Await client.Files.UploadSessionFinishAsync(cursor,
                                                                        New Files.CommitInfo(
                                                                        (folder + ("/" + ThisFilePath)),
                                                                        Files.WriteMode.Overwrite.Instance, False, Nothing, False), memStream)
                        Else
                            Await client.Files.UploadSessionAppendV2Async(cursor, body:=memStream)
                        End If
                    End If
                    idx += 1
                    Application.DoEvents()
                    Progress1.Value = CInt((idx / numChunks) * 100)
                    Progress1.ToolTipText = Progress1.Value & "%"
                Loop
                If Progress1.Value = 100 Then
                    Progress1.Value = 0
                    Progress1.ToolTipText = Progress1.Value & "%"
                End If
            End Using
        Catch ex As DropboxException
            MsgBox(ex.Message)
        End Try
    End Function

I already have another function returns Access-Token and stores it in My.Settings.AccessToken. In my Form, I call this function to upload the File :

Private Async Sub DropboxToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles DropboxToolStripMenuItem.Click
        Dim DropThis As New Drobbox
        Dim NewBakFile As String = "MYFILE.EXT" & Now.Date.ToShortDateString
        Try
            If ToolStripProgressBar1.Value <> 100 Then
                Try
                    IO.File.Copy("ThisDB.accdb", NewBakFile, True)
                Catch ex As IO.IOException
                    MsgBox("Error Copy : " & ex.Message)
                End Try
                ToolStripProgressBar1.Visible = True
                BackupToolStripMenuItem.Enabled = False
                'I obtain and store Access-Token here.
                Await DropThis.ChunkUpload(NewBakFile, ToolStripProgressBar1)
                BackupToolStripMenuItem.Enabled = True
                ToolStripProgressBar1.Visible = False
                DropLblUid.Text = ("Uploaded successfully. (" & Now.ToString("hh:mm:ss tt") & ")")
                Try
                    IO.File.Delete(NewBakFile)
                Catch ex As IO.IOException
                    MsgBox("Delete Error : " & ex.Message)
                End Try
            End If
        Catch ex As IO.IOException
            MsgBox(ex.Message)
        Finally
            DropboxToolStripMenuItem.Enabled = True
        End Try
    End Sub

My question is : How to Pause/Resume/Stop uploading the file ?

Update (1) : I have found this article about Upload/Cancel/Pause, I will take a look..... That method was not helpful

Update (2) : I'm trying to come up with a work around method as @Greg suggested.

Answer 1

The Dropbox API "upload session" functionality is a way to upload large files by doing so in pieces. The app creates one "upload session" per large file that it needs to upload, by initially calling UploadSessionStartAsync. Each upload session is valid for 48 hours.

Each call to UploadSessionStartAsync, UploadSessionAppendV2Async, UploadSessionFinishAsync can contain one consecutive piece of the file.

If you wish to pause the upload session, you can do so by inserting whatever flow control you want between the calls to any of those three methods. As long as you then continue running the code using the same cursor, within 48 hours, you can then continue and finish the upload session.