多线程挂起主线程，按顺序进行

Question

我遇到了一个多线程ping问题，它挂断了我的主线程。在调试这个问题时，我注意到当主线程挂起时，它正在启动每个线程，并移动到下一个线程进行ping。基本上，它必须ping 5个不同的IP地址，如果它们都关闭了，我的整个线程就会挂断20-30秒。我正在使用BeginInvoke，但它似乎仍然不能正常工作。

另一个奇怪的地方是，我在每个线程的末尾都添加了一个消息框，只是为了看看它们是如何完成的。我有5个线程，每个线程的末尾都会弹出一个消息框，上面写着"完成"。好吧，它不会只弹出5次，而是会出现10次，就像它运行了两次一样。通常我在这些线程中没有消息框，它只是在那里让我尝试弄清楚发生了什么，但我被难住了。

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

这是我的足迹：

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

这里的问题是您再次调用相同的方法，这些方法应该在线程中运行。这会导致ping请求再次发送，但这一次代码在UI线程上运行(因此它会冻结)。您应该确保只调用更新UI的代码。

这是可选的，但我建议您使用扩展方法为您进行调用检查，因为这将提高可读性，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，如果您的目标是.NETFramework4.0(或更高版本)，您可以使用lambda表达式快速生成内联委托：

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，如果您的目标是.NETFramework3.5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，不需要在代码的其余部分检查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，那么您只需要一个UpdatePingStatusDelegate委托，如果您只需要使用一个整数来更新所有线程的状态。

请参阅And和AndAlso之间的差异。