ManagementEventWatcher.WaitForNextEvent 方法

定义

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。Waits for the next event that matches the specified query to arrive, and then returns it.

public:
 System::Management::ManagementBaseObject ^ WaitForNextEvent();
public System.Management.ManagementBaseObject WaitForNextEvent ();
member this.WaitForNextEvent : unit -> System.Management.ManagementBaseObject
Public Function WaitForNextEvent () As ManagementBaseObject

返回

一个 ManagementBaseObject,它表示刚到达的事件。A ManagementBaseObject representing the newly arrived event.

示例

下面的示例演示在创建Win32_Process的实例时客户端如何收到通知,因为事件类是 __InstanceCreationEvent的。The following example shows how the client receives notification when an instance of Win32_Process is created because the event class is __InstanceCreationEvent. 有关详细信息,请参阅Windows Management Instrumentation文档。For more information, see the Windows Management Instrumentation documentation. 客户端通过调用 WaitForNextEvent 方法来同步接收事件。The client receives events synchronously by calling the WaitForNextEvent method. 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。This example can be tested by starting a process, such as Notepad, while the example code is running.

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 将仅等待指定时间段内的下一个事件;否则,会阻止 API,直到下一个事件发生。If the event watcher object contains options with a specified time-out, the API will wait for the next event only for the specified amount of time; otherwise, the API will be blocked until the next event occurs.

.NET Framework 安全性.NET Framework Security

对直接调用方的完全信任。Full trust for the immediate caller. 此成员不能由部分信任的代码使用。This member cannot be used by partially trusted code. 有关详细信息,请参阅从部分受信任的代码使用库For more information, see Using Libraries from Partially Trusted Code.

适用于