EventQuery 类

定义

命名空间:

System.Management

程序集:

System.Management.dll

包:

System.Management v8.0.0

Source:

ManagementQuery.cs

表示一个 WMI 事件查询。

public ref class EventQuery : System::Management::ManagementQuery

public class EventQuery : System.Management.ManagementQuery

type EventQuery = class
    inherit ManagementQuery

Public Class EventQuery
Inherits ManagementQuery

继承

Object

ManagementQuery

EventQuery

派生

System.Management.WqlEventQuery

示例

下面的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
        EventQuery query = new EventQuery();
        query.QueryString = "SELECT * FROM" +
            " __InstanceCreationEvent WITHIN 1 " +
            "WHERE TargetInstance isa \"Win32_Process\"";

        // Initialize an event watcher and subscribe to events
        // that match this query
        ManagementEventWatcher watcher =
            new ManagementEventWatcher(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 EventQuery
        query.QueryString = "SELECT * FROM" & _
            " __InstanceCreationEvent WITHIN 1 " & _
            "WHERE TargetInstance isa ""Win32_Process"""

        ' Initialize an event watcher and subscribe to events 
        ' that match this query
        Dim watcher As New ManagementEventWatcher(query)
        ' times watcher.WaitForNextEvent in 5 seconds
        watcher.Options.Timeout = New TimeSpan(0, 0, 50)

        ' 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

构造函数

EventQuery()	初始化 EventQuery 类的新实例。 这是无参数构造函数。
EventQuery(String)	为指定的查询初始化 EventQuery 类的新实例。
EventQuery(String, String)	根据指定的语言和查询初始化 EventQuery 类的新实例。

属性

QueryLanguage	获取或设置查询字符串中使用的查询语言，该语言定义查询字符串的格式。 (继承自 ManagementQuery)
QueryString	以文本格式获取或设置查询。 (继承自 ManagementQuery)

方法

Clone()	返回对象的一个副本。
Equals(Object)	确定指定对象是否等于当前对象。 (继承自 Object)
GetHashCode()	作为默认哈希函数。 (继承自 Object)
GetType()	获取当前实例的 Type。 (继承自 Object)
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
ParseQuery(String)	分析查询字符串并相应地设置属性值。 如果查询有效，将分析查询的类名属性和条件属性。 (继承自 ManagementQuery)
ToString()	返回表示当前对象的字符串。 (继承自 Object)