EventQuery クラスとは何？わかりやすく解説 Weblio辞書

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.NET Framework クラスライブラリリファレンス

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EventQuery クラス

WMI (Windows Management Instrumentation) イベントクエリを表します。

名前空間: System.Management
アセンブリ: System.Management (system.management.dll 内)
構文

Visual Basic (宣言)

Public Class EventQuery
    Inherits ManagementQuery

Visual Basic (使用法)

Dim instance As EventQuery

public class EventQuery : ManagementQuery

C++

public ref class EventQuery : public
 ManagementQuery

public class EventQuery extends ManagementQuery

JScript

public class EventQuery extends
 ManagementQuery

使用例

イベントクラスが __InstanceCreationEvent であるために、Win32_Process のインスタンスが作成されたときにクライアントが通知を受信するしくみを説明する例を次に示します。詳細については、MSDN ライブラリ (http://msdn.microsoft.com/library/ja) で Windows Management Instrumentation に関するドキュメントを参照してください。クライアントは WaitForNextEvent メソッドを呼び出して、イベントを同期的に受信します。この例は、コード例の実行中にメモ帳などのプロセスを開始することでテストできます。

Visual Basic

Imports System
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 'EventWatcherPolling

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;
    }
}