VB.NET - 在单独的线程中工作以防止表单挂起

Question

我有一个非常简单的表单，其中有一个按钮可以触发我创建的子程序，该子程序从 ActiveDirectory 收集数据并将其添加到 Excel 工作表中。

问题是，当我单击此按钮时，整个表单都会挂起。所以我认为收集数据并将其添加到 Excel 工作表的操作应该在它自己的线程中运行，这样表单就不会挂起。如果添加一个进度条可能会很棒。 然而，进度条位于项目运行后启动的主用户窗体中。

我需要做什么才能达到我想要的效果？

编辑：添加了我的一些代码。我有一个 MainForm.vb 和一个 CodeFile.vb。 我想要 CodeFile.vb 中的大部分代码，这样它会更整洁。

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

            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

请注意 CodeFile.vb 中的 ExportFromAD Sub。这就是实际做的工作。在将数据添加到 Excel 的 For every 循环中，我放置了 MainForm.MyBackgroundWorker.ReportProgress(i * 10)。

问题是，它实际上并没有更新表单上的标签。我觉得这很奇怪，因为表格并没有真正悬挂或任何东西。它是否试图访问不同的线程或其他什么？意思是，表单在它自己的线程上运行，无法从我的第二个线程访问？

Answer 1

最好的选择是使用 BackgroundWorker 因为此类是专为这种精确的用例而设计的。

这还允许您回调表单以更新状态栏。

Answer 2

您需要使用 BackgroundWorker 类。要将数据传递回表单的进度栏，请将 WorkerReportsProgress 属性设置为 true 并处理 ProgressChanged 事件以设置进度栏的值。从长时间运行的方法中，您可以像这样发送进度：

backgroundworker.ReportProgress(10)