ErrorEventHandler Delegate
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Represents the method that will handle the Error event of a FileSystemWatcher object.
public delegate void ErrorEventHandler(System::Object ^ sender, ErrorEventArgs ^ e);
public delegate void ErrorEventHandler(object sender, ErrorEventArgs e);
type ErrorEventHandler = delegate of obj * ErrorEventArgs -> unit
Public Delegate Sub ErrorEventHandler(sender As Object, e As ErrorEventArgs)
- sender
- Object
The source of the event.
An ErrorEventArgs object that contains the event data.
The following code example shows how to create a FileSystemWatcher
object to monitor file changes (creates, deletes, renames, changes) occurring on a disk drive. The example also shows how to properly receive error notifications.
using System;
using System.IO;
class Program
{
static void Main(string[] args)
{
// Create a FileSystemWatcher to monitor all files on drive C.
FileSystemWatcher fsw = new FileSystemWatcher("C:\\");
// Watch for changes in LastAccess and LastWrite times, and
// the renaming of files or directories.
fsw.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
| NotifyFilters.FileName |NotifyFilters.DirectoryName;
// Register a handler that gets called when a
// file is created, changed, or deleted.
fsw.Changed += new FileSystemEventHandler(OnChanged);
fsw.Created += new FileSystemEventHandler(OnChanged);
fsw.Deleted += new FileSystemEventHandler(OnChanged);
// Register a handler that gets called when a file is renamed.
fsw.Renamed += new RenamedEventHandler(OnRenamed);
// Register a handler that gets called if the
// FileSystemWatcher needs to report an error.
fsw.Error += new ErrorEventHandler(OnError);
// Begin watching.
fsw.EnableRaisingEvents = true;
Console.WriteLine("Press \'Enter\' to quit the sample.");
Console.ReadLine();
}
// This method is called when a file is created, changed, or deleted.
private static void OnChanged(object source, FileSystemEventArgs e)
{
// Show that a file has been created, changed, or deleted.
WatcherChangeTypes wct = e.ChangeType;
Console.WriteLine("File {0} {1}", e.FullPath, wct.ToString());
}
// This method is called when a file is renamed.
private static void OnRenamed(object source, RenamedEventArgs e)
{
// Show that a file has been renamed.
WatcherChangeTypes wct = e.ChangeType;
Console.WriteLine("File {0} {2} to {1}", e.OldFullPath, e.FullPath, wct.ToString());
}
// This method is called when the FileSystemWatcher detects an error.
private static void OnError(object source, ErrorEventArgs e)
{
// Show that an error has been detected.
Console.WriteLine("The FileSystemWatcher has detected an error");
// Give more information if the error is due to an internal buffer overflow.
if (e.GetException().GetType() == typeof(InternalBufferOverflowException))
{
// This can happen if Windows is reporting many file system events quickly
// and internal buffer of the FileSystemWatcher is not large enough to handle this
// rate of events. The InternalBufferOverflowException error informs the application
// that some of the file system events are being lost.
Console.WriteLine(("The file system watcher experienced an internal buffer overflow: " + e.GetException().Message));
}
}
}
Imports System.IO
Module Module1
Sub Main()
' Create a FileSystemWatcher to monitor all files on drive C.
Dim fsw As New FileSystemWatcher("C:\")
' Watch for changes in LastAccess and LastWrite times, and
' the renaming of files or directories.
fsw.NotifyFilter = (NotifyFilters.LastAccess Or NotifyFilters.LastWrite _
Or NotifyFilters.FileName Or NotifyFilters.DirectoryName)
' Register a handler that gets called when a
' file is created, changed, or deleted.
AddHandler fsw.Changed, New FileSystemEventHandler(AddressOf OnChanged)
' The commented line of code below is a shorthand of the above line.
' AddHandler fsw.Changed, AddressOf OnChanged
' NOTE: The shorthand version is used in the remainder of this code.
' FileSystemEventHandler
AddHandler fsw.Created, AddressOf OnChanged
' FileSystemEventHandler
AddHandler fsw.Deleted, AddressOf OnChanged
' Register a handler that gets called when a file is renamed.
' RenamedEventHandler
AddHandler fsw.Renamed, AddressOf OnRenamed
' Register a handler that gets called if the
' FileSystemWatcher needs to report an error.
' ErrorEventHandler
AddHandler fsw.Error, AddressOf OnError
' Begin watching.
fsw.EnableRaisingEvents = True
' Wait for the user to quit the program.
Console.WriteLine("Press 'Enter' to quit the sample.")
Console.ReadLine()
End Sub
' This method is called when a file is created, changed, or deleted.
Private Sub OnChanged(ByVal source As Object, ByVal e As FileSystemEventArgs)
' Show that a file has been created, changed, or deleted.
Dim wct As WatcherChangeTypes = e.ChangeType
Console.WriteLine("File {0} {1}", e.FullPath, wct.ToString())
End Sub
' This method is called when a file is renamed.
Private Sub OnRenamed(ByVal source As Object, ByVal e As RenamedEventArgs)
' Show that a file has been renamed.
Dim wct As WatcherChangeTypes = e.ChangeType
Console.WriteLine("File {0} {2} to {1}", e.OldFullPath, e.FullPath, wct.ToString())
End Sub
' This method is called when the FileSystemWatcher detects an error.
Private Sub OnError(ByVal source As Object, ByVal e As ErrorEventArgs)
' Show that an error has been detected.
Console.WriteLine("The FileSystemWatcher has detected an error")
' Give more information if the error is due to an internal buffer overflow.
If TypeOf e.GetException Is InternalBufferOverflowException Then
' This can happen if Windows is reporting many file system events quickly
' and internal buffer of the FileSystemWatcher is not large enough to handle this
' rate of events. The InternalBufferOverflowException error informs the application
' that some of the file system events are being lost.
Console.WriteLine( _
"The file system watcher experienced an internal buffer overflow: " _
+ e.GetException.Message)
End If
End Sub
End Module
When you create an ErrorEventHandler delegate, you identify the method that will handle the event. To associate the event with your event-handling method, add an instance of the delegate to the event. The event-handling method is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see Handling and Raising Events.
Get |
Gets an object that represents the method represented by the specified delegate. |
Product | Versions |
---|---|
.NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
.NET Framework | 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET Standard | 2.0, 2.1 |
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