多线程haning up主线程，按顺序排列。

Question

我遇到了悬挂主线程的多线程ping问题。在调试问题时，我注意到当主线程被挂起时，它正在启动每个线程并移动到下一个ping。基本上它必须ping 5个不同的IP地址，如果它们全部停止，我的整个线程会挂起20到30秒。我使用的是BeginInvoke，但它似乎仍然无法正常工作。

另一个奇怪的是，我在每个帖子的末尾添加了一个消息框，只是为了看看它们是如何完成的。我有5个帖子，每个帖子的末尾都会弹出一个消息框，说“完成”。＃34;好吧，它不会突然出现5次，而是会出现10次，就像它跑了两次一样。通常情况下，我没有在这些主题中设置消息框，我只是在那里尝试弄清楚发生了什么，但我很难过。

这将获取IP地址并启动线程：

Private Sub PingThreadStart()

    Host = zeroStoreNum


    IP = "10."
    Select Case (Host.Substring(0, 1))
        Case "0"
            IP = IP & "10."
        Case "1"
            IP = IP & "11."
        Case "2"
            IP = IP & "12."
        Case "3"
            IP = IP & "13."
        Case "4"
            IP = IP & "14."
        Case "5"
            IP = IP & "15."
        Case "6"
            IP = IP & "16."
        Case "7"
            IP = IP & "17."
        Case "8"
            IP = IP & "18."
        Case "9"
            IP = IP & "19."
    End Select

    Select Case (Host.Substring(1, 1))
        Case "0"
            'IP = IP & "0"
        Case "1"
            IP = IP & "1"
        Case "2"
            IP = IP & "2"
        Case "3"
            IP = IP & "3"
        Case "4"
            IP = IP & "4"
        Case "5"
            IP = IP & "5"
        Case "6"
            IP = IP & "6"
        Case "7"
            IP = IP & "7"
        Case "8"
            IP = IP & "8"
        Case "9"
            IP = IP & "9"
    End Select

    Select Case (Host.Substring(2, 1))
        Case "0"
            IP = IP & "0."
        Case "1"
            IP = IP & "1."
        Case "2"
            IP = IP & "2."
        Case "3"
            IP = IP & "3."
        Case "4"
            IP = IP & "4."
        Case "5"
            IP = IP & "5."
        Case "6"
            IP = IP & "6."
        Case "7"
            IP = IP & "7."
        Case "8"
            IP = IP & "8."
        Case "9"
            IP = IP & "9."
    End Select
    If Host = 100 Then
        IP = "10.10.100."
    End If
    If Host = 200 Then
        IP = "10.11.100."
    End If
    If Host = 300 Then
        IP = "10.12.100."
    End If
    If Host = 400 Then
        IP = "10.13.100."
    End If
    If Host = 500 Then
        IP = "10.14.100."
    End If
    If Host = 600 Then
        IP = "10.15.100."
    End If
    If Host = 700 Then
        IP = "10.16.100."
    End If
    If Host = 800 Then
        IP = "10.17.100."
    End If
    If Host = 900 Then
        IP = "10.18.100."
    End If

    lblIPschemeCH.Text = IP & "X"

    SonicWALL = IP & "1"
    primary = IP & "2"
    secondary = IP & "3"

    Dim PingPublicTry As Thread = New Thread(AddressOf PingPublicTH)
    Dim PingSWpublicTry As Thread = New Thread(AddressOf PingSWpublicTH)
    Dim PingDotOneTry As Thread = New Thread(AddressOf PingDotOneTH)
    Dim PingDotTwoTry As Thread = New Thread(AddressOf PingDotTwoTH)
    Dim PingDotThreeTry As Thread = New Thread(AddressOf PingDotThreeTH)

    PingPublicTry.IsBackground = True
    PingSWpublicTry.IsBackground = True
    PingDotOneTry.IsBackground = True
    PingDotTwoTry.IsBackground = True
    PingDotThreeTry.IsBackground = True


    If ModemPublic = "DHCP" Or SonicWALLPublic = "DHCP" Then
        PingDotOneTry.Start()
        PingDotTwoTry.Start()
        PingDotThreeTry.Start()
    Else
        PingPublicTry.Start()
        PingSWpublicTry.Start()
        PingDotOneTry.Start()
        PingDotTwoTry.Start()
        PingDotThreeTry.Start()
    End If



End Sub

这是我的脚步：

    Private Sub PingPublicTH()
    Dim pingactmodem As New System.Net.NetworkInformation.Ping
    Dim pingretmodem As System.Net.NetworkInformation.PingReply
    Dim speedmodem As Integer

    Try
        pingretmodem = pingactmodem.Send(ModemPublic)
        speedmodem = pingretmodem.RoundtripTime
    Catch ex As Exception

    End Try

    If (lblModCh.InvokeRequired) Then

        Dim show As New PingPublicDel(AddressOf PingPublicTH)
        Me.lblModCh.BeginInvoke(show)
    Else
        If speedmodem >= 1 And speedmodem <= 500 Then
            lblModCh.BackColor = Color.Green
        ElseIf speedmodem >= 501 And speedmodem <= 1500 Then
            lblModCh.BackColor = Color.Orange
        ElseIf speedmodem >= 1501 Then
            lblModCh.BackColor = Color.Red
        ElseIf speedmodem = 0 Then
            lblModCh.BackColor = Color.Black

        End If
    End If
    MessageBox.Show("Done modem")


End Sub
Private Sub PingSWpublicTH()
    Dim pingactswp As New System.Net.NetworkInformation.Ping

    Dim pingretswp As System.Net.NetworkInformation.PingReply
    Dim speedswp As Integer

    Try
        pingretswp = pingactswp.Send(SonicWALLPublic)
        speedswp = pingretswp.RoundtripTime
    Catch ex As Exception
    End Try

    If (lbSWPCh.InvokeRequired) Then

        Dim show As New PingSwPublicDel(AddressOf PingSWpublicTH)
        Me.lbSWPCh.BeginInvoke(show)
    Else
        If speedswp >= 1 And speedswp <= 500 Then
            lbSWPCh.BackColor = Color.Green
        ElseIf speedswp >= 501 And speedswp <= 1500 Then
            lbSWPCh.BackColor = Color.Orange
        ElseIf speedswp >= 1501 Then
            lbSWPCh.BackColor = Color.Red
        ElseIf speedswp = 0 Then
            lbSWPCh.BackColor = Color.Black

        End If

    End If
    MessageBox.Show("Done swp")

End Sub
Private Sub PingDotOneTH()
    Dim pingact1 As New System.Net.NetworkInformation.Ping
    Dim pingret1 As System.Net.NetworkInformation.PingReply
    Dim speed1 As Integer



    pingret1 = pingact1.Send(SonicWALL)
    speed1 = pingret1.RoundtripTime

    If (lblSWch.InvokeRequired) Then

        Dim show As New PingDotOneDel(AddressOf PingDotOneTH)
        Me.lblSWch.BeginInvoke(show)

    Else

        If speed1 >= 1 And speed1 <= 500 Then
            lblSWch.Text = (speed1)
            lblSWch.BackColor = Color.Green
        ElseIf speed1 >= 501 And speed1 <= 1500 Then
            lblSWch.Text = (speed1)
            lblSWch.BackColor = Color.Orange
        ElseIf speed1 >= 1501 Then
            lblSWch.Text = (speed1)
            lblSWch.BackColor = Color.Red
        ElseIf speed1 = 0 Then
            lblSWch.Text = "Down"
            lblSWch.BackColor = Color.Black

        End If
    End If
    MessageBox.Show("Done .1")
End Sub
Private Sub PingDotTwoTH()
    Dim pingact2 As New System.Net.NetworkInformation.Ping
    Dim pingret2 As System.Net.NetworkInformation.PingReply
    Dim Speed2 As Integer


    pingret2 = pingact2.Send(primary)
    Speed2 = pingret2.RoundtripTime

    If (lblMainpcCH.InvokeRequired) Then
        Dim show As New PingDotTwoDel(AddressOf PingDotTwoTH)
        Me.lblMainpcCH.BeginInvoke(show)

    Else

        If Speed2 >= 1 And Speed2 <= 500 Then
            lblMainpcCH.Text = (Speed2)
            lblMainpcCH.BackColor = Color.Green
        ElseIf Speed2 >= 501 And Speed2 <= 1500 Then
            lblMainpcCH.Text = (Speed2)
            lblMainpcCH.BackColor = Color.Orange
        ElseIf Speed2 >= 1501 Then
            lblMainpcCH.Text = (Speed2)
            lblMainpcCH.BackColor = Color.Red
        ElseIf Speed2 = 0 Then
            lblMainpcCH.Text = "Down"
            lblMainpcCH.BackColor = Color.Black

        End If

    End If
    MessageBox.Show("Done .2")
End Sub
Private Sub PingDotThreeTH()
    Dim pingact3 As New System.Net.NetworkInformation.Ping
    Dim pingret3 As System.Net.NetworkInformation.PingReply
    Dim speed3 As Integer



    pingret3 = pingact3.Send(secondary)
    speed3 = pingret3.RoundtripTime


    If (lblSecondch.InvokeRequired) Then

        Dim show As New PingDotThreeDel(AddressOf PingDotThreeTH)

        Me.lblSecondch.BeginInvoke(show)

    Else

        If speed3 >= 1 And speed3 <= 500 Then
            lblSecondch.Text = (speed3)
            lblSecondch.BackColor = Color.Green
        ElseIf speed3 >= 501 And speed3 <= 1500 Then
            lblSecondch.Text = (speed3)
            lblSecondch.BackColor = Color.Orange
        ElseIf speed3 >= 1501 Then
            lblSecondch.Text = (speed3)
            lblSecondch.BackColor = Color.Red
        ElseIf speed3 = 0 Then
            lblSecondch.Text = "Down"
            lblSecondch.BackColor = Color.Black

        End If

    End If
    MessageBox.Show("Done .3")
End Sub

Answer 1

这里的问题是你再次调用相同的方法，它们应该在线程中运行。这导致ping请求再次发送，但这次代码在UI线程上运行（因此它冻结的原因）。您应确保仅调用更新UI的代码。

这是可选的，但我建议您使用extension method为您执行调用检查，因为它会提高可读性，但也会减少您必须编写的代码量：

Imports System.Runtime.CompilerServices

Public Module Extensions
    <Extension()> _
    Public Sub InvokeIfRequired(ByVal Control As Control, ByVal Method As [Delegate], ByVal ParamArray Parameters As Object())
        If Parameters Is Nothing OrElse _
            Parameters.Length = 0 Then Parameters = Nothing 'If Parameters is null or has a length of zero then no parameters should be passed.
        If Control.InvokeRequired = True Then
            Control.Invoke(Method, Parameters)
        Else
            Method.DynamicInvoke(Parameters)
        End If
    End Sub
End Module

现在，如果您定位 .NET Framework 4.0 （或更高版本），则可以使用lambda expression作为快速内联委托：

Me.InvokeIfRequired( _
    Sub()
        If speedmodem >= 1 AndAlso speedmodem <= 500 Then
            lblModCh.BackColor = Color.Green
        ElseIf speedmodem >= 501 And speedmodem <= 1500 Then
            lblModCh.BackColor = Color.Orange
        ElseIf speedmodem >= 1501 Then
            lblModCh.BackColor = Color.Red
        ElseIf speedmodem = 0 Then
            lblModCh.BackColor = Color.Black
        End If
    End Sub)

但是，如果您定位 .NET Framework 3.5 或更低版本，则必须以正常方式创建委托：

Private Delegate Sub UpdatePingStatusDelegate(ByVal speedmodem As Integer)

Private Sub PingPublicTH()
    ...your code...

    Me.InvokeIfRequired(New UpdatePingStatusDelegate(AddressOf UpdateStatusPublicTH), speedmodem)
End Sub

Private Sub UpdateStatusPublicTH(ByVal speedmodem As Integer)
    If speedmodem >= 1 AndAlso speedmodem <= 500 Then
        lblModCh.BackColor = Color.Green
    ElseIf speedmodem >= 501 And speedmodem <= 1500 Then
        lblModCh.BackColor = Color.Orange
    ElseIf speedmodem >= 1501 Then
        lblModCh.BackColor = Color.Red
    ElseIf speedmodem = 0 Then
        lblModCh.BackColor = Color.Black
    End If
End Sub

注意：

• 使用扩展方法InvokeIfRequired时，您无需在代码的其余部分中检查Control.InvokeRequired。您只需要对扩展方法进行一次调用，它就会为您进行检查。

• 如果您使用我的第二种方法，您只需要一个UpdatePingStatusDelegate委托，如果您只需要一个整数来更新所有线程的状态。

另请参阅the difference between And and AndAlso。