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VB.NET - Doing work in separate thread to prevent Form from hanging

开发者 https://www.devze.com 2023-03-03 17:59 出处:网络
I have a really simple form with a button that fires a Sub I created which gathers data from ActiveDirectory and adds it to an Excel Sheet.

I have a really simple form with a button that fires a Sub I created which gathers data from ActiveDirectory and adds it to an Excel Sheet.

The problem is, when I click this button the whole form hangs. So I figured the operation that gathers the data and adding it to the Excel sheet should be run in it's own thread, so that the form won't hang. Possibly it would be great to add a progressbar as well. The progressbar however is located at the Main userform that starts up once the projects is run.

What do I need to do in order to get this the way I want?

Edit: Added some of my code. I've got one MainForm.vb and one CodeFile.vb. I want most of the code in the CodeFile.vb so it's tidier.

MainForm.vb

Imports User_edit.CodeFile
Imports System.ComponentModel

Public Class MainForm
    Private Sub btnImportData_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnImportData.Click
        If MyBackgroundWorker.IsBusy <> True Then
            MyBackgroundWorker.RunWorkerAsync()
        End If
    End Sub

    Private Sub BackgroundWorker_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles MyBackgroundWorker.DoWork
        ExportADUsers()
    End Sub

    Private Sub BackgroundWorker_ProgressChanged(ByVal sender As System.Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles MyBackgroundWorker.ProgressChanged
        statusBarLabel.Text = (e.ProgressPercentage.ToString)
    End Sub

    Private Sub BackgroundWorker_RunWorkerCompleted(ByVal sender As System.Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles MyBackgroundWorker.RunWorkerCompleted
        statusBarLabel.Text = "Finished"
    End Sub
End Class

CodeFile.vb

Imports System.DirectoryServices
Imports System.ComponentModel
Imports System.Threading

Module CodeFile
    Public Sub ExportADUsers()
        MainForm.MyBackgroundWorker.WorkerReportsProgress = True
        MainForm.MyBackgroundWorker.WorkerSupportsCancellation = True

        Dim i As Integer

        Dim objRootDSE, strRoot, strfilter, strAttributes, strScope
            objRootDSE = GetObject("LDAP://RootDSE")
            strRoot = objRootDSE.GET("DefaultNamingContext")
            strfilter = "(&(objectCategory=Person)(objectClass=User))"
            strAttributes = "mail,userPrincipalName,givenName,sn," & _
              "initials,displayName,physicalDeliveryOfficeName," & _
              "telephoneNumber,mail,wWWHomePage,profilePath," & _
              "scriptPath,homeDirectory,homeDrive,title,department," & _
              "company,manager,homePhone,pager,mobile," & _
              "facsimileTelephoneNumber,ipphone,info," & _
              "streetAddress,postOfficeBox,l,st,postalCode,c"
            'Scope of the search.  Change to "onelevel" if you didn't want to search child OU's
            MainForm.statusBarLabel.Text = "Collecting data"
        strScope = "subtree"

            Dim cn, cmd, rs
            cn = CreateObject("ADODB.Connection")
            cmd = CreateObject("ADODB.Command")

            cn.open("Provider=ADsDSOObject;")
            cmd.ActiveConnection = cn
            cmd.commandtext = "<LDAP://" & strRoot & ">;" & strfilter & ";" & _
                                strAttributes & ";" & strScope

            rs = cmd.EXECUTE

            Dim objExcel, objWB, objSheet

       开发者_开发问答     objExcel = CreateObject("Excel.Application")
            objWB = objExcel.Workbooks.Add
        objSheet = objWB.Worksheets(1)

        For i = 0 To rs.Fields.Count - 1
            MainForm.MyBackgroundWorker.ReportProgress(i * 10)
            objSheet.Cells(1, i + 1).Value = rs.Fields(i).Name
            objSheet.Cells(1, i + 1).Font.Bold = True
        Next

            Dim strExportFile
            strExportFile = "C:\users\vsando\desktop\export.xls"

            objSheet.Range("A2").CopyFromRecordset(rs)
            objSheet.SaveAs(strExportFile)

            'Clean up
            rs.Close()
            cn.Close()
            objSheet = Nothing
            objWB = Nothing
            objExcel.Quit()
            objExcel = Nothing

    End Sub

Notice the ExportFromAD Sub I've got in the CodeFile.vb. This is what is actually doing the work. In the For each loop that adds data to the Excel is where I've put the MainForm.MyBackgroundWorker.ReportProgress(i * 10).

Problem is, it doesn't actually update the label on the form. Which I find pretty weird because the form isn't really hanging or anything. Is it trying to access a different thread or something? Meaning, the form is run on it's own thread which can't be accessed from my second thread?


Your best bet is to use a BackgroundWorker since this class is designed for this precise use-case.

This also allows you to call back to the form to update the status bar.


The BackgroundWorker class is what you need to use. For passing data back to the form's progress bar you set the WorkerReportsProgress property to true and handle the ProgressChanged event to set the progress bar's value. From the long running method you can send progress like this:

backgroundworker.ReportProgress(10)
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