How do I use VB Application.DoEvent? - vb.net

Question

I have a process that works well when it's running against small files but gives an "Message=Managed Debugging Assistant 'ContextSwitchDeadlock' : 'The CLR has been unable to transition from COM context 0xa5b8e0 to COM context 0xa5b828 for 60 seconds." error when running against large files. I'm pretty new to VB and did some investigating and found that using Application.DoEvent seemed to be recommended. I was hoping that someone could show me an example of how to use that. If I'm executing a Sub called "Process1", how would I use the DoEvent to prevent it from timing out. Ideally I'd like to add a progress bar as well but I have ot idea on that one either. I'd appreciate any help. Please keep it simple as I'm new to VB/VS.
This is the comment from my first question showing the code. Process1 calls a sub named ArchDtlCopyFile1 which scrolls through the values in a list view, copying the files named in the items to a different location. It then calls ArchDtlCheckCopy1 to scroll through the list view again to ensure that the copy was done. It then decides if the source file should be deleted and do it if required. Finally it inserts a row in an Access table documenting the change made.
Private Sub Process1()
If ReturnCode = 0 Then
ArchDtlCopyFile1()
Else
' MessageBox.Show("Error code coming in is: " & CStr(ReturnCode))
End If
If ReturnCode = 0 Then
ArchDtlCheckCopy1()
Else
' MessageBox.Show("Error code for check copy is: " & CStr(ReturnCode))
End If
End Sub
Private Sub ArchDtlCopyFile1()
intLVIndex = 0
' Copy the file from the source computer onto the NAS
Do While intLVIndex < intMaxFileIndex
Try
' Select the row from the LVFiles ListView, then move the first column (0) into strSourceFilePath and the last
' column (3) into strDestFilePath. Execute the CopyFile method to copy the file.
LVFiles.Items(intLVIndex).Selected = True
strSourceFilePath = LVFiles.SelectedItems(intLVIndex).SubItems(0).Text
strDestFilePath = LVFiles.SelectedItems(intLVIndex).SubItems(3).Text
My.Computer.FileSystem.CopyFile(strSourceFilePath, strDestFilePath, overwrite:=False)
Catch ex As Exception
' Even if there's an error with one file, we should continue trying to process the rest of the files
Continue Do
End Try
intLVIndex += 1
Loop
End Sub
Private Sub ArchDtlCheckCopy1()
intLVIndex = 0
intLVError = 0
' ' Check each file was copied onto the NAS
Do While intLVIndex < intMaxFileIndex
' Select the row from the LVFiles ListView, then move the last column (3) into strDestFilePath.
' Use the FileExists method to ensure the file was created on the NAS. If it was, call the
' ADetDelete Sub to delete the source file from the user's computer.
LVFiles.Items(intLVIndex).Selected = True
strSourceFilePath = LVFiles.SelectedItems(intLVIndex).SubItems(0).Text
strDestFilePath = LVFiles.SelectedItems(intLVIndex).SubItems(3).Text
strSourceFile = LVFiles.SelectedItems(intLVIndex).SubItems(1).Text
Try
If My.Computer.FileSystem.FileExists(strDestFilePath) Then
' Archive file was created so go ahead and delete the source file
'If strSourceFile = myCheckFile Then
' strDestFile = LVFiles.SelectedItems(intLVIndex).SubItems(3).Text
'End If
If RBArchive.Checked = True Then
ArchDtlDeleteFile(strSourceFilePath)
End If
PrepareDtlVariables()
ADtlAddRow()
Else
MessageBox.Show("File not found. " & strDestFilePath)
End If
Catch ex As Exception
ErrorCode = "ARC6"
MessageCode = "Error while checking file copy"
ReturnCode = 8
End Try
intLVIndex += 1
Loop
End Sub

Answer 1

Here's a simplified example:
Imports System.ComponentModel
Imports System.IO
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
BackgroundWorker1.WorkerReportsProgress = True
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Button1.Enabled = False
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
For i As Integer = 1 To 20
BackgroundWorker1.ReportProgress(i) ' you can pass anything out using the other overloaded ReportProgress()
System.Threading.Thread.Sleep(1000)
Next
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
' you can also use e.UserState to pass out ANYTHING
Label1.Text = e.ProgressPercentage
End Sub
Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
MessageBox.Show("Done!")
Button1.Enabled = True
End Sub
End Class