ManagementEventWatcher.WaitForNextEvent 方法

定义

命名空间:

System.Management

程序集:

System.Management.dll

包:

System.Management v8.0.0

Source:

ManagementEventWatcher.cs

等待出现下一个与指定的查询匹配的事件，然后将该事件返回。

public:
 System::Management::ManagementBaseObject ^ WaitForNextEvent();

public System.Management.ManagementBaseObject WaitForNextEvent ();

member this.WaitForNextEvent : unit -> System.Management.ManagementBaseObject

Public Function WaitForNextEvent () As ManagementBaseObject

返回

ManagementBaseObject

一个 ManagementBaseObject，它表示刚到达的事件。

示例

以下示例演示由于事件类__InstanceCreationEvent而创建 Win32_Process 实例时客户端如何接收通知。 有关详细信息，请参阅 Windows Management Instrumentation 文档。 客户端通过调用 WaitForNextEvent 方法来同步接收事件。 在运行此代码示例的同时，可以启动进程（如记事本）来测试此示例。

using System;
using System.Management;

// This example shows synchronous consumption of events.
// The client is blocked while waiting for events.

public class EventWatcherPolling
{
    public static int Main(string[] args)
    {
        // Create event query to be notified within 1 second of
        // a change in a service
        WqlEventQuery query =
            new WqlEventQuery("__InstanceCreationEvent",
            new TimeSpan(0,0,1),
            "TargetInstance isa \"Win32_Process\"");

        // Initialize an event watcher and subscribe to events
        // that match this query
        ManagementEventWatcher watcher =
            new ManagementEventWatcher();
        watcher.Query = query;
        // times out watcher.WaitForNextEvent in 5 seconds
        watcher.Options.Timeout = new TimeSpan(0,0,5);

        // Block until the next event occurs
        // Note: this can be done in a loop if waiting for
        //        more than one occurrence
        Console.WriteLine(
            "Open an application (notepad.exe) to trigger an event.");
        ManagementBaseObject e = watcher.WaitForNextEvent();

        //Display information from the event
        Console.WriteLine(
            "Process {0} has been created, path is: {1}",
            ((ManagementBaseObject)e
            ["TargetInstance"])["Name"],
            ((ManagementBaseObject)e
            ["TargetInstance"])["ExecutablePath"]);

        //Cancel the subscription
        watcher.Stop();
        return 0;
    }
}

Imports System.Management

' This example shows synchronous consumption of events. 
' The client is blocked while waiting for events. 

Public Class EventWatcherPolling
    Public Overloads Shared Function _
        Main(ByVal args() As String) As Integer

        ' Create event query to be notified within 1 second of 
        ' a change in a service
        Dim query As New WqlEventQuery( _
            "__InstanceCreationEvent", _
            New TimeSpan(0, 0, 1), _
            "TargetInstance isa ""Win32_Process""")

        ' Initialize an event watcher and subscribe to events 
        ' that match this query
        Dim watcher As New ManagementEventWatcher
        watcher.Query = query
        ' times watcher.WaitForNextEvent in 5 seconds
        watcher.Options.Timeout = New TimeSpan(0, 0, 5)

        ' Block until the next event occurs 
        ' Note: this can be done in a loop
        ' if waiting for more than one occurrence
        Console.WriteLine( _
          "Open an application (notepad.exe) to trigger an event.")
        Dim e As ManagementBaseObject = _
            watcher.WaitForNextEvent()

        'Display information from the event
        Console.WriteLine( _
            "Process {0} has created, path is: {1}", _
            CType(e("TargetInstance"), _
                ManagementBaseObject)("Name"), _
            CType(e("TargetInstance"), _
                ManagementBaseObject)("ExecutablePath"))

        'Cancel the subscription
        watcher.Stop()
        Return 0

    End Function 'Main
End Class

注解

如果事件观察程序对象包含具有指定超时的选项，则 API 将仅等待指定时间量的下一个事件;否则，将阻止 API，直到发生下一个事件。

.NET Framework 安全性

对直接调用方的完全信任。 此成员不能由部分信任的代码使用。 有关详细信息，请参阅 使用部分受信任的代码中的库。