本月我将向你展示如何使用 CLR 的 Thread 类来创建和管理你自己的线程。我也将讨论一些情节，在这些情节中创建和管理一个辅助线程比使用委托来异步执行一个方法更好一点。

创建线程

　　当你想创建一个新线程时，你可以创建一个 Thread 类的实例，它在 System.Threading 名字空间中定义。Thread 类的构造函数 以一个 ThreadStart 委托对象的引用为参数。在 Figure 1 的代码中你可以看到如何创建一个线程的两个例子。
　　正如你所看到的，对于创建一个新线程对象有一个普通句法和一个速记句法。Figure 1 中创建ThreadA 的技术示范了如何显式的创建一个绑定于 MyAsyncTask 方法的 ThreadStart 委托对象。创建 ThreadB 的技术使用更少的 键盘敲击达到同样的目的。那是因为当你写出下面的一行代码时，Visual Basic 编译器隐式的为你创建了一个 ThreadStart 委托对象：

	Dim ThreadB As New Thread(AddressOf TedsCode.MyAsyncTask)	

	Dim ThreadA As New TedsThreadClass(1, "Bob")
	ThreadA.Start();	

	Dim ThreadA As Thread
	ThreadA = New Thread(AddressOf TedsCode.MyAsyncTask)

	''*** do some work on primary thread

	''*** now block until secondary thread is done
	ThreadA.Join()	

• 需要执行一个长期运行的任务
• 需要调整某个线程的优先级
• 需要一个前台线程，它将保持托管桌面程序处于活动状态
• 需要一个单线程单元（STA）线程同单元线程COM对象一起工作

	Dim ThreadA As Thread
	ThreadA = New Thread(AddressOf TedsCode.MyAsyncTask)
	ThreadA.Priority = ThreadPriority.BelowNormal
	ThreadA.Start()	

	Dim ThreadA As Thread
	ThreadA = New Thread(AddressOf TedsCode.MyAsyncTask)
	ThreadA.IsBackground = True
	TheadA.Start()	

	Class MyApp
  	   
 Shared Sub Main()
               ''*** application code here
           End Sub
	End Class	

	Class MyApp
 	   

  	   Shared Sub Main()
    	      ''*** application code here
  	   End Sub
	End Class	

	Dim ThreadA As Thread
	ThreadA = New Thread(AddressOf TedsCode.MyAsyncTask)
	ThreadA.ApartmentState = ApartmentState.STA
	ThreadA.Start()

	''*** When you create a COM object, the CLR
	''*** will initialize ThreadA as an STA thread	

附：

Figure 1 创建辅助物理线程
Imports System
Imports System.Threading

Class MyApp
Shared Sub Main()

'*** long-hand syntax for creating a thread
Dim MyHandler As New ThreadStart(AddressOf TedsCode.MyAsyncTask)
Dim ThreadA As New Thread(MyHandler)
ThreadA.Start();

'*** short-hand syntax for creating a thread
Dim ThreadB As New Thread(AddressOf TedsCode.MyAsyncTask)
ThreadB.Start()

End Sub
End Class

--------------------------------------------------------------------------------
Figure 2 向异步方法传递参数
Imports System
Imports System.Threading

Class MyApp
Shared Sub Main()

Dim ThreadA As New TedsThreadClass(1, "Bob")
ThreadA.Start()

Dim ThreadB As New TedsThreadClass(2, "Betty")
ThreadB.Start()

End Sub
End Class

Class TedsThreadClass

'*** define custom fields and constructor with parameterized data
Protected x As Integer
Protected y As String
Sub New(ByVal X as Integer, ByVal Y As String)
Me.x = X
Me.y = Y
End Sub

'*** instance method used to run asynchronous task
Sub MyASyncTask()
'*** this code has access to x and y
End Sub

'*** encapsulated threading support
Protected InnerThread As New Thread(AddressOf Me.MyAsyncTask)
Public Sub Start()
InnerThread.Start()
End Sub

End Class