執行緒計時器
更新：2007 年 11 月
System.Threading.Timer 類別 (Class) 對定期會在個別執行緒上執行工作而言是很有用的。例如，您可以使用執行緒計時器來檢查狀態和資料庫的完整性，或備份重要的檔案。
執行緒計時器範例
下列範例每隔兩秒便會開啟工作，並使用旗標來初始化停止計時器的 Dispose 方法。這個範例會將狀態公佈於輸出視窗中，在測試程式碼之前可以按 CTRL+ALT+O 以顯示這個視窗。
Class StateObjClass
' Used to hold parameters for calls to TimerTask
Public SomeValue As Integer
Public TimerReference As System.Threading.Timer
Public TimerCanceled As Boolean
End Class
Sub RunTimer()
Dim StateObj As New StateObjClass
StateObj.TimerCanceled = False
StateObj.SomeValue = 1
Dim TimerDelegate As New Threading.TimerCallback(AddressOf TimerTask)
' Create a timer that calls a procedure every 2 seconds.
' Note: There is no Start method; the timer starts running as soon as
' the instance is created.
Dim TimerItem As New System.Threading.Timer(TimerDelegate, StateObj, _
2000, 2000)
StateObj.TimerReference = TimerItem ' Save a reference for Dispose.
While StateObj.SomeValue < 10 ' Run for ten loops.
System.Threading.Thread.Sleep(1000) ' Wait one second.
End While
StateObj.TimerCanceled = True ' Request Dispose of the timer object.
End Sub
Sub TimerTask(ByVal StateObj As Object)
Dim State As StateObjClass = CType(StateObj, StateObjClass)
' Use the interlocked class to increment the counter variable.
System.Threading.Interlocked.Increment(State.SomeValue)
System.Diagnostics.Debug.WriteLine("Launched new thread " & Now)
If State.TimerCanceled Then ' Dispose Requested.
State.TimerReference.Dispose()
System.Diagnostics.Debug.WriteLine("Done " & Now)
End If
End Sub
當 System.Windows.Forms.Timer 物件無法使用時 (例如在開發主控台應用程式時)，執行緒計時器便特別有用。