VB.NET 多线程同步有关问题_多核软件开发

VB.NET 多线程同步问题

VB.NET code

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 
         url = "http://topic.csdn.net/t/20041007/15/3431114" 
         Dim th As New System.Threading.Thread(AddressOf URL1) 
         th.Start() 
         MsgBox(shuju) 
     End Sub 
  
     Private Sub URL1() 
         Dim s As New System.Net.WebClient() 
         shuju = System.Text.Encoding.GetEncoding("gb2312").GetString(s.DownloadData(url)) 
     End Sub

第一次接触多线程。发现我点击玩按钮后 msgbox 直接给我弹出来了一个空内容~
也就是说下面的线程并没有执行结束但是 Button1_Click 里面的代码已经执行完毕了~

如果等待线程执行完毕后再执行 MsgBox(shuju)？？？

------解决方案--------------------------------------------------------

VB.NET code

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click        url = "http://topic.csdn.net/t/20041007/15/3431114"        Dim th As New System.Threading.Thread(AddressOf URL1)        th.Start()        While th.IsAlive            Application.DoEvents()            System.Threading.Thread.Sleep(5)        End While        MsgBox(shuju)    End Sub    Private Sub URL1()        Dim s As New System.Net.WebClient()        shuju = System.Text.Encoding.GetEncoding("gb2312").GetString(s.DownloadData(url))    End Sub
------解决方案--------------------------------------------------------
你把MsgBox放到线程里提示。。。就不卡了。本来也应该是子线程提示主线程完事的。。。

当然直接用MsgBox在子线程里好不好另说。
------解决方案--------------------------------------------------------
Public Class Form1
   Dim url As String
   Dim shuju As String
   Private Delegate Sub showMsgbox(ByVal msg As String)

   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
       url = "http://topic.csdn.net/t/20041007/15/3431114"
       Dim showmsgbox As showMsgbox = AddressOf URL1
       showmsgbox(url)
   End Sub

   Private Sub URL1()
       Dim s As New System.Net.WebClient()
       shuju = System.Text.Encoding.GetEncoding("gb2312").GetString(s.DownloadData(url))
       MsgBox(shuju)
   End Sub
End Class