Change the visibility of a panel (Windows Forms) - vb.net

Question

I leave it to you because I can't find a solution to my problem : /
Let me explain, when I press a button I display a panel containing other buttons, at the click of one of the buttons on the panel it should launch a method that will convert the selected files to pdf. As soon as the user has clicked on one of the buttons and confirmed the choice of file, I make my panel invisible and I then launch the conversion method.
The problem is that my panel disappears let's say by half (not entirely) because it launches the conversion method as quickly. I told myself that I was going to go through a secondary thread, however I cannot modify graphic elements on the second thread.
There is my code :
Private Sub PBFolder_Click(sender As Object, e As EventArgs) Handles PBFolder.Click
Try
Insert2Db("Debut de la fonction BTransforme_Click " + Environment.UserName.ToString, 1, 0, "ConvertFiles2PDF")
'Log("Debut de la fonction BTransforme_Click")
Dim OFD As New FolderBrowserDialog
If OFD.ShowDialog = Windows.Forms.DialogResult.OK Then
PanFileFolder.Visible = False
ConvertFileFolder(False, OFD.SelectedPath.ToString)
End If
Catch ex As Exception
'Log("Error " + ex.Message)
Insert2Db("Error " + ex.Message + "User : " + Environment.UserName.ToString, 0, 3, "ConvertFiles2PDF")
Finally
Insert2Db("function BTransforme_Click Terminé " + Environment.UserName.ToString, 1, 0, "ConvertFiles2PDF")
'Log("function BTransforme_Click Terminé")
End Try
LAppOne.Visible = True
GifLoad.Visible = False
Button1.Enabled = True
BLog.Enabled = True
End Sub
As you can see I hide my panel thanks to line: PanFileFolder.Visible = False then I launch my conversion method convertFileFolder (False, OFD.SelectedPath.ToString)
I have put 2 images to illustrate my problem.
the 1st image shows you the panel that appears on click:
the second image shows you the problem that this causes me to choose the folder:
When it has finished converting the files, the panel disappears correctly at this time.
Do you have an idea to solve this problem thank you in advance ;)

Answer 1

I told myself that I was going to go through a secondary thread,
however I cannot modify graphic elements on the second thread.
That is exactly what will fix your problem; ConvertFileFolder() needs to be running in a different thread so that GUI can refresh itself and be responsive to user interact. You can update the GUI from that secondary thread using Invoke() calls.
Here I've added Async to the Button click handler, then we Await the ConvertFileFolder() FUNCTION, which now returns a Task:
Private Async Sub PBFolder_Click(sender As Object, e As EventArgs) Handles PBFolder.Click
' ... other code ...
Using OFD As New FolderBrowserDialog
If OFD.ShowDialog = DialogResult.OK Then
PanFileFolder.Visible = False
Await ConvertFileFolder(False, OFD.SelectedPath.ToString)
End If
End Using
' ... other code ...
End Sub
Public Function ConvertFileFolder(ByVal someFlag As Boolean, ByVal someString As String) As Task
Return Task.Run(Sub()
' ... long running code in here ...
For i As Integer = 1 To 10
System.Threading.Thread.Sleep(1000) ' some "work"
' whenever you need to update the GUI, use Invoke()
Dim value As String = i.ToString
Me.Invoke(Sub()
Label1.Text = value
End Sub)
Next
End Sub)
End Function