VB.NET并行与分布式编程(7)-线程池[2]

在此，我们仅以GetAvailableThreads为例：

当 GetAvailableThreads 返回时，workerThreads 指定的变量包含可以启动的其他辅助线程的数目，而 completionPortThreads 指定的变量包含可以启动的其他异步 I/O 线程的数目

代码如下:

Imports System
Imports System.Threading
Imports System.Runtime.InteropServices
Imports System.Diagnostics
Imports System.Diagnostics.ThreadState


Module Module1
    Dim jg As Long = 0
    Public Class TaskInfo
        Public Handle As RegisteredWaitHandle = Nothing
        Public OtherInfo As String = "default"
        Public ev As AutoResetEvent
    End Class


    <MTAThread()> _
    Sub Main()








        '定义AutoResetEvent和RegisteredWaitHandle对象
        Dim myHandle As RegisteredWaitHandle = Nothing


        Dim ti As New TaskInfo()
        ti.ev = New AutoResetEvent(False)
        ti.OtherInfo = "deepfuture test"
        '注册等待,等待线程的任务就是定时取计算结果，如果没有计算完成，就继续等待
        ti.Handle = ThreadPool.RegisterWaitForSingleObject( _
           ti.ev, _
           New WaitOrTimerCallback(AddressOf mythreadrun), _
           ti, _
           100, _
           False _
       )
        Console.Write("{0},开始执行线程，主线程{1}正在计算结果", Now.ToLongTimeString, Thread.CurrentThread.ManagedThreadId)
        '等待并执行其它代码
        For mynum = 1 To 100
            jg += mynum
            Thread.Sleep(10)
            Console.WriteLine("主线程{0}正在运行.....当前计算结果为{1}", Now.ToLongTimeString, jg)
        Next
        Console.WriteLine("主线程  " & Now.ToLongTimeString & "线程计算完毕!")
        '设置为终止状态，触发回调
        ti.ev.Set()
        Thread.Sleep(20)


    End Sub
    Public Sub mythreadrun(ByVal state As Object, ByVal timedOut As Boolean)
        '本线程的任务是的计算完成后显示结果，没计算完成时，做其它工作，
        '在这里其他工作就是显示一个"."
        Dim ti As TaskInfo = CType(state, TaskInfo)
        Dim workerThreads As Integer
        Dim portThreads As Integer
        If timedOut Then
            '时间到，仍没计算完毕，为非终止状态 
            Console.WriteLine("等待时间到，计算没有完毕，继续等待...")
            ThreadPool.GetAvailableThreads(workerThreads, portThreads)
            Console.WriteLine("目前可以启动的工作线程的数目{0},目前可以启动的异步IO线程的数目{1}", workerThreads, portThreads)
        Else
            If Not ti.Handle Is Nothing Then
                '已经终止
                ti.Handle.Unregister(Nothing)
            End If
            Console.WriteLine("主线程{0}运行完成.....读取最终计算结果为{1}", Now.ToLongTimeString, jg)
        End If
    End Sub
End Module