EventWatcherOptions.BlockSize Property
Definition
Important
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Gets or sets the block size for block operations. When waiting for events, this value specifies how many events to wait for before returning.
public:
property int BlockSize { int get(); void set(int value); };
public int BlockSize { get; set; }
member this.BlockSize : int with get, set
Public Property BlockSize As Integer
Property Value
An integer value indicating the block size for a block of operations.
Examples
The following example shows how the client receives notification when an instance of Win32_Process is created because the event class is __InstanceCreationEvent. For more information, see the Windows Management Instrumentation documentation. The client receives events synchronously by calling the WaitForNextEvent method. 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
string query = "SELECT * FROM" +
" __InstanceCreationEvent WITHIN 1 " +
"WHERE TargetInstance isa \"Win32_Process\"";
// Event options
EventWatcherOptions eventOptions = new
EventWatcherOptions();
eventOptions.Timeout = System.TimeSpan.MaxValue;
// return after 1 event is received
eventOptions.BlockSize = 1;
// Initialize an event watcher and subscribe to events
// that match this query
ManagementEventWatcher watcher =
new ManagementEventWatcher("root\\CIMV2", query,
eventOptions);
// 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 String
query = "SELECT * FROM" & _
" __InstanceCreationEvent WITHIN 1 " & _
"WHERE TargetInstance isa ""Win32_Process"""
' Event options
Dim eventOptions As New EventWatcherOptions
eventOptions.Timeout = System.TimeSpan.MaxValue
' return after 1 event is received
eventOptions.BlockSize = 1
' Initialize an event watcher and subscribe to events
' that match this query
Dim watcher As New ManagementEventWatcher( _
"root\CIMV2", query, eventOptions)
' 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
Remarks
Property Value
The default value is 1.
.NET Framework Security
Full trust for the immediate caller. This member cannot be used by partially trusted code. For more information, see Using Libraries from Partially Trusted Code.
Applies to
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