EventLog Constructors

Definition

Namespace:

System.Diagnostics

Assembly:

System.Diagnostics.EventLog.dll

Initializes a new instance of the EventLog class.

Overloads

EventLog()	Initializes a new instance of the EventLog class. Does not associate the instance with any log.
EventLog(String)	Initializes a new instance of the EventLog class. Associates the instance with a log on the local computer.
EventLog(String, String)	Initializes a new instance of the EventLog class. Associates the instance with a log on the specified computer.
EventLog(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.

EventLog()

Initializes a new instance of the EventLog class. Does not associate the instance with any log.

public:
 EventLog();

public EventLog ();

Public Sub New ()

Examples

The following example creates the source MySource if it does not already exist, and writes an entry to the event log MyNewLog.

#using <System.dll>

using namespace System;
using namespace System::Diagnostics;
using namespace System::Threading;
int main()
{
   
   // Create the source, if it does not already exist.
   if (  !EventLog::SourceExists( "MySource" ) )
   {
      //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" );
      Console::WriteLine( "CreatingEventSource" );
      // The source is created.  Exit the application to allow it to be registered.
      return 0;
   }

   
   // Create an EventLog instance and assign its source.
   EventLog^ myLog = gcnew EventLog;
   myLog->Source = "MySource";
   
   // Write an informational entry to the event log.    
   myLog->WriteEntry( "Writing to event log." );
}

using System;
using System.Diagnostics;
using System.Threading;

class MySample{

    public static void Main(){

        // Create the source, if it does not already exist.
        if(!EventLog.SourceExists("MySource"))
        {
             //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");
            Console.WriteLine("CreatedEventSource");
            Console.WriteLine("Exiting, execute the application a second time to use the source.");
            // The source is created.  Exit the application to allow it to be registered.
            return;
        }

        // Create an EventLog instance and assign its source.
        EventLog myLog = new EventLog();
        myLog.Source = "MySource";

        // Write an informational entry to the event log.
        myLog.WriteEntry("Writing to event log.");
    }
}

Option Explicit
Option Strict

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")
            Console.WriteLine("CreatingEventSource")
            'The source is created.  Exit the application to allow it to be registered.
            Return
        End If
        
        ' Create an EventLog instance and assign its source.
        Dim myLog As New EventLog()
        myLog.Source = "MySource"
        
        ' Write an informational entry to the event log.    
        myLog.WriteEntry("Writing to event log.")
    End Sub
End Class

Remarks

Before calling WriteEntry, specify the Source property of the EventLog instance. If you are only reading Entries from the log, you can alternatively specify only the Log and MachineName properties.

Note

If you do not specify a MachineName, the local computer (".") is assumed.

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

Property	Initial Value
Source	An empty string ("").
Log	An empty string ("").
MachineName	The local computer (".").

See also

• Source
• Log
• MachineName
• Entries
• WriteEntry
• WriteEvent
• EventLogEntry

EventLog(String)

Initializes a new instance of the EventLog class. Associates the instance with a log on the local computer.

public:
 EventLog(System::String ^ logName);

public EventLog (string logName);

new System.Diagnostics.EventLog : string -> System.Diagnostics.EventLog

Public Sub New (logName As String)

Parameters

logName

String

The name of the log on the local computer.

Exceptions

ArgumentNullException

The log name is null.

ArgumentException

The log name is invalid.

Examples

The following example reads entries in the event log, "myNewLog", on the local computer.

#using <System.dll>

using namespace System;
using namespace System::Diagnostics;
using namespace System::Threading;
int main()
{
    // Create the source, if it does not already exist.
   if (  !EventLog::SourceExists( "MySource" ) )
   {
      //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" );
      Console::WriteLine( "CreatingEventSource" );
      // The source is created.  Exit the application to allow it to be registered.
      return 0;
   }

   
   // Create an EventLog instance and assign its log name.
   EventLog^ myLog = gcnew EventLog( "myNewLog" );
   
   // Read the event log entries.
   System::Collections::IEnumerator^ myEnum = myLog->Entries->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      EventLogEntry^ entry = safe_cast<EventLogEntry^>(myEnum->Current);
      Console::WriteLine( "\tEntry: {0}", entry->Message );
   }
}

using System;
using System.Diagnostics;
using System.Threading;

class MySample
{
    public static void Main()
    {
        // Create the source, if it does not already exist.
        if (!EventLog.SourceExists("MySource"))
        {
            //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");
            Console.WriteLine("CreatedEventSource");
            Console.WriteLine("Exiting, execute the application a second time to use the source.");
            // The source is created.  Exit the application to allow it to be registered.
            return;
        }

        // Create an EventLog instance and assign its log name.
        EventLog myLog = new EventLog("myNewLog");

        // Read the event log entries.
        foreach (EventLogEntry entry in myLog.Entries)
        {
            Console.WriteLine("\tEntry: " + entry.Message);
        }
    }
}

Option Explicit
Option Strict

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")
            Console.WriteLine("CreatingEventSource")
            'The source is created.  Exit the application to allow it to be registered.
            Return
        End If

        Dim myLog As New EventLog("myNewLog")
        
        ' Read the event log entries.
        Dim entry As EventLogEntry
        For Each entry In  myLog.Entries
            Console.WriteLine((ControlChars.Tab & "Entry: " & entry.Message))
        Next entry
    End Sub
End Class

Remarks

This overload sets the Log property to the logName parameter. Before calling WriteEntry, specify the Source property of the EventLog instance. If you are only reading Entries from the log, you can alternatively specify only the Log and MachineName properties.

Note

If you do not specify a MachineName, the local computer (".") is assumed. This overload of the constructor specifies the Log property, but you can change this before reading the Entries property.

If the source you specify in the Source property is unique from other sources on the computer, a subsequent call to WriteEntry creates a log with the specified name, if it does not already exist.

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

Property	Initial Value
Source	An empty string ("").
Log	The logName parameter.
MachineName	The local computer (".").

See also

• Source
• Log
• MachineName
• Entries
• WriteEntry
• WriteEvent
• EventLogEntry

EventLog(String, String)

Initializes a new instance of the EventLog class. Associates the instance with a log on the specified computer.

public:
 EventLog(System::String ^ logName, System::String ^ machineName);

public EventLog (string logName, string machineName);

new System.Diagnostics.EventLog : string * string -> System.Diagnostics.EventLog

Public Sub New (logName As String, machineName As String)

Parameters

logName

String

The name of the log on the specified computer.

machineName

String

The computer on which the log exists.

Exceptions

ArgumentNullException

The log name is null.

ArgumentException

The log name is invalid.

-or-

The computer name is invalid.

Examples

The following example reads entries in the event log, "myNewLog", on the computer "myServer".

#using <System.dll>

using namespace System;
using namespace System::Diagnostics;
using namespace System::Threading;
int main()
{
   // Create the source, if it does not already exist.
   if (  !EventLog::SourceExists( "MySource" ) )
   {
      //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", "myServer" );
      Console::WriteLine( "CreatingEventSource" );
      // The source is created.  Exit the application to allow it to be registered.
      return 0;
   }

   // Create an EventLog instance and assign its log name.
   EventLog^ myLog = gcnew EventLog( "myNewLog","myServer" );
   
   // Read the event log entries.
   System::Collections::IEnumerator^ myEnum = myLog->Entries->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      EventLogEntry^ entry = safe_cast<EventLogEntry^>(myEnum->Current);
      Console::WriteLine( "\tEntry: {0}", entry->Message );
   }
}

using System;
using System.Diagnostics;
using System.Threading;

class MySample1
{
    public static void Main()
    {
        // Create the source, if it does not already exist.
        if (!EventLog.SourceExists("MySource"))
        {
            //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", "myServer");
            Console.WriteLine("CreatedEventSource");
            Console.WriteLine("Exiting, execute the application a second time to use the source.");
            // The source is created.  Exit the application to allow it to be registered.
            return;
        }
        // Create an EventLog instance and assign its log name.
        EventLog myLog = new EventLog("myNewLog", "myServer");

        // Read the event log entries.
        foreach (EventLogEntry entry in myLog.Entries)
        {
            Console.WriteLine("\tEntry: " + entry.Message);
        }
    }
}

Option Explicit
Option Strict

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", "myServer")
            Console.WriteLine("CreatingEventSource")
            'The source is created.  Exit the application to allow it to be registered.
            Return
        End If

        ' Create an EventLog instance and assign its log name.
        Dim myLog As New EventLog("myNewLog", "myServer")
        
        ' Read the event log entries.
        Dim entry As EventLogEntry
        For Each entry In  myLog.Entries
            Console.WriteLine((ControlChars.Tab & "Entry: " & entry.Message))
        Next entry
    End Sub
End Class

Remarks

This overload sets the Log property to the logName parameter and the MachineName property to the machineName parameter. Before calling WriteEntry, specify the Source property of the EventLog. If you are only reading Entries from the log, you can alternatively specify only the Log and MachineName properties.

Note

This overload of the constructor specifies the Log and MachineName properties, but you can change either before reading the Entries property.

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

Property	Initial Value
Source	An empty string ("").
Log	The logName parameter.
MachineName	The machineName parameter.

See also

• Source
• Log
• MachineName
• Entries
• WriteEntry
• WriteEvent
• EventLogEntry

EventLog(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.

public:
 EventLog(System::String ^ logName, System::String ^ machineName, System::String ^ source);

public EventLog (string logName, string machineName, string source);

new System.Diagnostics.EventLog : string * string * string -> System.Diagnostics.EventLog

Public Sub New (logName As String, machineName As String, source As String)

Parameters

logName

String

The name of the log on the specified computer.

machineName

String

The computer on which the log exists.

source

String

The source of event log entries.

Exceptions

ArgumentNullException

The log name is null.

ArgumentException

The log name is invalid.

-or-

The computer name is invalid.

Examples

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

#using <System.dll>

using namespace System;
using namespace System::Diagnostics;
using namespace System::Threading;
int main()
{
   // Create the source, if it does not already exist.
   if (  !EventLog::SourceExists( "MySource" ) )
   {
      //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");
      Console::WriteLine( "CreatingEventSource" );
      // The source is created.  Exit the application to allow it to be registered.
      return 0;
   }
   
   // Create an EventLog instance and assign its source.
   EventLog^ myLog = gcnew EventLog( "myNewLog",".","MySource" );
   
   // Write an entry to the log.        
   myLog->WriteEntry( String::Format( "Writing to event log on {0}", myLog->MachineName ) );
}

using System;
using System.Diagnostics;
using System.Threading;

class MySample2
{
    public static void Main()
    {
        // Create the source, if it does not already exist.
        if (!EventLog.SourceExists("MySource"))
        {
            //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");
            Console.WriteLine("CreatedEventSource");
            Console.WriteLine("Exiting, execute the application a second time to use the source.");
            // The source is created.  Exit the application to allow it to be registered.
            return;
        }
        // Create an EventLog instance and assign its source.
        EventLog myLog = new EventLog("myNewLog", ".", "MySource");

        // Write an entry to the log.
        myLog.WriteEntry("Writing to event log on " + myLog.MachineName);
    }
}

Option Strict
Option Explicit

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")
            Console.WriteLine("CreatingEventSource")
            'The source is created.  Exit the application to allow it to be registered.
            Return
        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
End Class

Remarks

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.

Property	Initial Value
Source	The source parameter.
Log	The logName parameter.
MachineName	The machineName parameter.

See also

• Source
• Log
• MachineName
• Entries
• WriteEntry
• WriteEvent
• EventLogEntry