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EventLog.WriteEntry Method (String, String, EventLogEntryType, Int32)

Writes an entry with the given message text and application-defined event identifier to the event log, using the specified registered event source.

Namespace:  System.Diagnostics
Assembly:  System (in System.dll)

Public Shared Sub WriteEntry ( _
	source As String, _
	message As String, _
	type As EventLogEntryType, _
	eventID As Integer _


Type: System.String
The source by which the application is registered on the specified computer.
Type: System.String
The string to write to the event log.
Type: System.Diagnostics.EventLogEntryType
One of the EventLogEntryType values.
Type: System.Int32
The application-specific identifier for the event.


The source value is an empty string ("").

- or -

The source value is Nothing.

- or -

eventID is less than zero or greater than UInt16.MaxValue.

- or -

The message string is longer than 31,839 bytes (32,766 bytes on Windows operating systems before Windows Vista).

- or -

The source name results in a registry key path longer than 254 characters.


The registry key for the event log could not be opened.


type is not a valid EventLogEntryType.


The operating system reported an error when writing the event entry to the event log. A Windows error code is not available.

Use this method to write an entry with an application-defined eventID to the event log, using a source already registered as an event source for the appropriate log. The eventID, along with the source, uniquely identify an event. Each application can define its own numbered events and the description strings to which they map. Event viewers present these strings to the user to help the user understand what went wrong and suggest what actions to take.


The message string cannot contain %n, where n is an integer value (for example, %1), because the event viewer treats it as an insertion string. Because an Internet Protocol, version 6 (IPv6) address can contain this character sequence, you cannot log an event message that contains an IPv6 address.

In addition to the event identifier, this overload of WriteEntry lets you specify an EventLogEntryType for the event being written to the event log. The type is indicated by an icon and text in the Type column in the Event Viewer for a log. This parameter indicates whether the event type is error, warning, information, success audit, or failure audit.

You must create and configure the event source before writing the first entry with the source. Create the new event source during the installation of your application. This allows time for the operating system to refresh its list of registered event sources and their configuration. If the operating system has not refreshed its list of event sources, and you attempt to write an event with the new source, the write operation will fail. You can configure a new source using an EventLogInstaller, or using the CreateEventSource method. You must have administrative rights on the computer to create a new event source.

The source must be configured either for writing localized entries or for writing direct strings. The WriteEntry method writes the given string directly to the event log; it does not use a localizable message resource file. Use the WriteEvent method to write events using a localized message resource file.

If your application writes entries using both resource identifiers and string values, you must register two separate sources. For example, configure one source with resource files, and then use that source in the WriteEvent method to write entries using resource identifiers to the event log. Then create a different source without resource files, and use that source in the WriteEntry method to write strings directly to the event log using that source.


If the message parameter contains a NUL character, the message in the event log is terminated at the NUL character.

' Create the source, if it does not already exist.
If Not EventLog.SourceExists("MySource") Then
   EventLog.CreateEventSource("MySource", "myNewLog")
   Console.WriteLine("Creating EventSource")
End If

' Set the 'description' for the event.
Dim myMessage As String = "This is my event."
Dim myEventLogEntryType As EventLogEntryType = EventLogEntryType.Warning
Dim myApplicationEventId As Integer = 100

' Write the entry in the event log.
Console.WriteLine("Writing to EventLog.. ")
EventLog.WriteEntry("MySource", myMessage, myEventLogEntryType, myApplicationEventId)

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.