多线程学习笔记

现在手上有一些历史的VB项目,是工控方面PLC控制的. 代码用了很多DoEvent 和时间等待. DoEvent的最大问题的不知道流程跳到哪里去了.

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

MSComm1.InBufferCount = 0 MSComm1.Output = nSendTemp DoEvents    Start = timeGetTime           Do While timeGetTime - Start < 500 '在毫秒内连续读PLC '16是返回位的长度,要等它返回完之后,才能继续下一步         If MSComm1.InBufferCount >= 16 Then                           Dim readTemp() As Byte                 readTemp = MSComm1.Input                 Dim nTemp(20) As Long                 If DispatchPlcData_Wr(readTemp, nTemp, 2) = False Then                 '读PLC错                         nData(0) = 0                         nData(1) = 0                         GoTo EndFunc                 Else                         nData(0) = nTemp(0)                         nData(1) = nTemp(1)                         GetAddressData = True                                                       Exit Function                 End If         End If         DoEvents Loop

 

所以,不得以要用C#重新改造,重新捡起多线程.之前写WinForm比较少,重新学习一遍多线程.

1. IO密集型的,尽量不要用多线程,而是用异步方法.因为IO比CPU慢太多了.CPU只需要偶尔发个指令过去,然后在异步方法完成时处理一下就好了.