多线程

1. 利用委托启用不带返回值线程

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

Dim mAction As New Action(Of String)(AddressOf DoSomething)

'mAction("1")'直接调用委托，这种方式会阻塞线程

'mAction.Invoke("2")'调用委托的Invoke 方法，这种方式与直接调用委托一样，会阻塞线程

'线程执行完后，会先来这行这个函数

Dim mCallback As AsyncCallback = New AsyncCallback(Sub(ByVal ar As AsyncResult)

Dim RetS As String = ar.AsyncState '这里会得到的结果是BeginInvoke传进来的第三个参数："hhhhh"

'Me.Text = RetS '更新不了，因为这里还是属于线程的一部分

End Sub)

'调用委托的BeginInvoke 方法，这种方式不会阻塞线程

Dim asyncResult As IAsyncResult = mAction.BeginInvoke("3", mCallback, "hhhhh")

'这里可以做一些其他事情

'

'

'asyncResult.AsyncWaitHandle.WaitOne() '阻塞线程

asyncResult.AsyncWaitHandle.WaitOne(-1) '阻塞线程，一直等待

'asyncResult.AsyncWaitHandle.WaitOne(150) '阻塞线程，最多等待150ms

End Sub

Public Sub DoSomething(ByVal mS As String)

Dim d As Double

For i As Integer = 0 To 1000000000

d += i Mod 2

Next

End Sub

1. 利用委托启动带返回值的线程

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click

Dim mFun As New Func(Of String, String)(AddressOf DoSomething1)

Dim mCallback As AsyncCallback = New AsyncCallback(Sub(ByVal ar As AsyncResult)

'可以在回调中获取结果

Dim OutS1 As String = mFun.EndInvoke(ar) '这里的结果是123999

End Sub)

Dim asyncResult As IAsyncResult = mFun.BeginInvoke("123", mCallback, "hhhhh")

'也可以在外部获取结果，调用这个时会阻塞主线程，等待线程结束

Dim OutS As String = mFun.EndInvoke(asyncResult) '这里的结果是123999

End Sub

Public Function DoSomething1(ByVal mS As String) As String

Dim d As Double

For i As Integer = 0 To 1000000000

d += i Mod 2

Next

Return mS & "999"

End Function

1.  
2.