How to: Determine If an Event Source Exists 

  • Article

Once you identify a source for a particular event log, this information is stored in the server's registry files until you remove that source. If you try to re-register a source that has already been registered as a valid source for a given log, the system raises a run-time error. You can use the SourceExists method to determine whether or not a particular source has already been registered.

To determine if a source has already been registered

  • Call the SourceExists method, specifying the source name to query.

    The following example shows how to determine if a source using the string MyApp1 is already registered, and to register it with the Application log if it is not.

    If Not EventLog.SourceExists("MyApp1") Then
    EventLog.CreateEventSource("MyApp1", "Application")
End If

    if (!System.Diagnostics.EventLog.SourceExists("MyApp1"))
    System.Diagnostics.EventLog.CreateEventSource(
       "MyApp1", "Application");

    if (!System.Diagnostics.EventLog.SourceExists("MyApp1"))
{
   System.Diagnostics.EventLog.CreateEventSource("MyApp1",
       "Application");
}

    To determine if a source is registered on a remote computer, specify the computer name as a second parameter. The following code shows an example:

    If Not EventLog.SourceExists("MyApp1", "myserver") Then
    Dim create As New EventSourceCreationData("MyApp1", "Application")
    create.MachineName = "myserver"
    EventLog.CreateEventSource(create)
End If

    EventSourceCreationData sourceData = new EventSourceCreationData("MyApp1", "Application");
sourceData.MachineName = "myserver";
if (!System.Diagnostics.EventLog.SourceExists("MyApp1", "myserver"))
    System.Diagnostics.EventLog.CreateEventSource(sourceData);

    if (!System.Diagnostics.EventLog.SourceExists("MyApp1", "myserver"))
{
   System.Diagnostics.EventLog.CreateEventSource(
      "MyApp1", "Application", "myserver");
}

See Also

Tasks

How to: Remove an Event Source
How to: Add Your Application as a Source of Event Log Entries
Walkthrough: Exploring Event Logs, Event Sources, and Entries