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EventLog Constructor (String, String, String)

Initializes a new instance of the EventLog class. Associates the instance with a log on the specified computer and creates or assigns the specified source to the EventLog.

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

Public Sub New ( _
	logName As String, _
	machineName As String, _
	source As String _
Dim logName As String 
Dim machineName As String 
Dim source As String 

Dim instance As New EventLog(logName, _
	machineName, source)


Type: System.String

The name of the log on the specified computer

Type: System.String

The computer on which the log exists.

Type: System.String

The source of event log entries.


The log name is Nothing.


The log name is invalid.


The computer name is invalid.

This constructor sets the Log property to the logName parameter, the MachineName property to the machineName parameter, and the Source property to the source parameter. The Source property is required when writing to an event log. However, if you are only reading from an event log, only the Log and MachineName properties are required (as long as the event log on the server has a source already associated with it). If you are only reading from the event log, another overload of the constructor might suffice.

The following table shows initial property values for an instance of EventLog.


Initial Value


The source parameter.


The logName parameter.


The machineName parameter.

The following example writes an entry to an event log, "MyNewLog", on the local computer, using the source "MySource".

Option Strict
Option Explicit

Imports System
Imports System.Diagnostics
Imports System.Threading

Class MySample
    Public Shared Sub Main()
        If Not EventLog.SourceExists("MySource") Then 
            ' Create the source, if it does not already exist. 
            ' An event log source should not be created and immediately used. 
            ' There is a latency time to enable the source, it should be created 
            ' prior to executing the application that uses the source. 
            ' Execute this sample a second time to use the new source.
            EventLog.CreateEventSource("MySource", "MyNewLog")
            'The source is created.  Exit the application to allow it to be registered. 
        End If 
        ' Create an EventLog instance and assign its source. 
        Dim myLog As New EventLog("myNewLog", ".", "MySource")

        ' Write an entry to the log.        
        myLog.WriteEntry(("Writing to event log on " & myLog.MachineName))
    End Sub ' Main 
End Class ' MySample

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

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