.net编程时在线程里使用Form上的控件的问题-优快云博客

本文介绍如何在VB.NET中安全地从后台线程更新Form上的ListView控件。通过使用Delegate和Invoke方法，可以避免直接修改UI组件导致的问题。示例代码展示了具体的实现过程。

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在写VB.net时，遇到要在线程里改变Form上的ListView控件中的信息，动手做起来才发现并不是那么容易。因为微软的框架并不鼓励在线程里直接访问Form上的控件。因为这样会改变UI进程的正常执行。如果必须这样做，需要在线程中使用Invoke函数或者InvokeBegin函数。下面是一个例子：

Imports System.Threading

Public Class Form1
Delegate Sub AddListItem(ByVal IPString As String, ByVal ScanPort As Integer)
Public myDelegate As AddListItem
Public OpenPortCount As Integer = 0

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
myDelegate = New AddListItem(AddressOf AddListItemMethod)
End Sub

Private Sub Start_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Start_Button.Click
Dim mythread As Thread
mythread = New Thread(New ThreadStart(AddressOf ThreadFunction))
mythread.Start()

End Sub

Private Sub ThreadFunction()
Dim mythread As Thread
mythread = New Thread(New ThreadStart(AddressOf DoScanThread))
mythread.Start()
End Sub 'ThreadFunction

Private Sub DoScanThread()
Dim myThreadClassObject As New ScanThreadClass(Me)
myThreadClassObject.run()
End Sub

Public Sub AddListItemMethod(ByVal IPString As String, ByVal scanport As Integer)
ListView_Result.Items.Add(IPString, OpenPortCount) 'ScanIP.ToString(), 0)
ListView_Result.Items(OpenPortCount).SubItems.Add(scanport.ToString())
OpenPortCount += 1
End Sub 'AddListItemMethod

End Class

Public Class ScanThreadClass
Private myFormControl1 As Form1

Public Sub New(ByVal myForm As Form1)
myFormControl1 = myForm
End Sub 'New

Public Sub run()
myFormControl1.Invoke(myFormControl1.myDelegate, New Object() {"11", 123})
End Sub

End Class

主要注意的就是Invoke的调用和Delegate的定义。