Question

我已经构建了一个程序，用于检查应用程序是否已启用。如果启用，它将执行BackgroundWorker，如果没有，它将通知用户并立即关闭。它适用于我的计算机，但对其他人来说，它没有错误地完成代码。

这是我的代码：

Dim Status As String = ""
Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
    If Status = "Enabled" Or Status = "Disabled" Then
    Else
        Status = WebBrowser1.Document.GetElementById(Account & "Flag").InnerText.ToString
        If Status = "Enabled" Then
            BackgroundWorker1.RunWorkerAsync()
        ElseIf Status = "Disabled" Then
            MessageBox.Show("Disabled", "System", MessageBoxButtons.OK)
            Close()
        Else
            Status = ""
        End If
    End If
End Sub

对我而言，我认为它并没有让BackgroundWorker开始工作。我已经通过在第一行代码之后放置MsgBox("Code 1 Success")而在第二行代码之后放置MsgBox("Code 2 Success")来测试代码，依此类推。并且它到达BackgroundWorker1.RunWorkerAsync()代码，但它不执行BackgroundWorker下的代码。

这是BackgroundWorker1代码：

Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    Label1.Text = "Status: Checking"
    Label1.ForeColor = Color.FromKnownColor(KnownColor.Highlight)
    Try
        Dim mysqlconnection As MySqlConnection = New MySqlConnection("server=85.10.205.173;port=3306;username='" & User & "';password='" & Pass & "'")
        Dim mysqlcommand As MySqlCommand = Nothing
        Dim mysqldatareader As MySqlDataReader = Nothing
        mysqlconnection.Open()
        Using table As DataTable = New DataTable
            Using command As MySqlCommand = New MySqlCommand("Select * from login.accounts where Username = 'Jake';", mysqlconnection)
                Using adapter As MySqlDataAdapter = New MySqlDataAdapter(command)
                    adapter.Fill(table)
                End Using
            End Using

            For Each row As DataRow In table.Rows
                If row("Flag") = "enable" Then
                    Label1.Text = "Status: Enabled"
                    Label1.ForeColor = Color.Green
                    Button1.Enabled = False
                    Button2.Enabled = True
                    ProgressBar1.Visible = False
                Else
                    Label1.Text = "Status: Disabled"
                    Label1.ForeColor = Color.OrangeRed
                    Button1.Enabled = True
                    Button2.Enabled = False
                    ProgressBar2.Visible = False
                End If
            Next
        End Using
        mysqlconnection.Close()
    Catch ex As Exception
        Threading.Thread.Sleep(1000)
        Label1.Text = "No Internet Connection"
    End Try
End Sub

我知道它没有达到此代码，因为Label1.Text没有改变，如果它到达代码的这一部分，那一定是“状态：正在检查”。

我的代码有什么问题？同样，它适用于我的计算机，但对其他人而言，它没有。非常感谢任何帮助！

Answer 1

根据MSDN，

您必须小心不要操纵任何用户界面对象你的DoWork事件处理程序。而是与用户界面进行通信通过BackgroundWorker事件。

可能第一行导致错误。最好在UI线程上调用它。见How to: Make Thread-Safe Calls to Windows Forms Controls

附注：

DoWork中的循环似乎不对。您正在寻找行中的标志并设置启用和禁用状态，如果多行已设置标志或未设置，该怎么办？如果查询每次只返回1行，那么您不需要这里的循环
您应该在DoWork事件处理程序中进行一些登录，以便了解内部实际发生的情况。
通常我们不会在DoWork事件处理程序中处理异常，而是使用RunWorkerCompleted事件来告诉您进程中是否发生了异常。无论如何，最好使用此事件以了解该过程已完成。

Answer 2

我终于开始工作了

以下是我使用的代码：

Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    BackgroundWorker1.ReportProgress(10)
    Dim mysqlconnection As MySqlConnection = New MySqlConnection("server=85.10.205.173;port=3306;username='" & User & "';password='" & Pass & "'")
    BackgroundWorker1.ReportProgress(20)
    Dim mysqlcommand As MySqlCommand = Nothing
    BackgroundWorker1.ReportProgress(30)
    Dim mysqldatareader As MySqlDataReader = Nothing
    BackgroundWorker1.ReportProgress(40)
    mysqlconnection.Open()
    BackgroundWorker1.ReportProgress(50)
    Using table As DataTable = New DataTable
        BackgroundWorker1.ReportProgress(60)
        Using command As MySqlCommand = New MySqlCommand("Select * from my.accounts where Username = 'Ray';", mysqlconnection)
            BackgroundWorker1.ReportProgress(70)
            Using adapter As MySqlDataAdapter = New MySqlDataAdapter(command)
                BackgroundWorker1.ReportProgress(80)
                adapter.Fill(table)
                BackgroundWorker1.ReportProgress(90)
            End Using
        End Using

        For Each row As DataRow In table.Rows
            If row("Flag") = "enable" Then
                e.Result = "1"
                BackgroundWorker1.ReportProgress(100)
            Else
                e.Result = "0"
                BackgroundWorker1.ReportProgress(100)
            End If
        Next
    End Using
    mysqlconnection.Close()
End Sub

Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
    If e.ProgressPercentage = 10 Then
        Label1.Text = "Status: Checking"
        Label1.ForeColor = Color.FromKnownColor(KnownColor.Highlight)
    End If
    ProgressBar1.Value = e.ProgressPercentage
    ProgressBar1.Refresh()
End Sub

Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
    Threading.Thread.Sleep(500)
    ProgressBar1.Value = 0
    If e.Result = "1" Then
        Label1.Text = "Status: Enabled"
        Label1.ForeColor = Color.Green
        Button1.Enabled = False
        Button2.Enabled = True
    ElseIf e.Result = "0" Then
        Label1.Text = "Status: Disabled"
        Label1.ForeColor = Color.OrangeRed
        Button1.Enabled = True
        Button2.Enabled = False
    Else
        MessageBox.Show("Unknown output: " & e.Result & " . Closing", "", MessageBoxButtons.OK, MessageBoxIcon.Error)
        Close()
    End If
End Sub

谢谢@sallushan

程序不适用于不同的设备

2 个答案: