EventListener Class
Provides methods for enabling and disabling events from event sources.
Namespace: System.Diagnostics.Tracing
Assembly: mscorlib (in mscorlib.dll)
The EventListener type exposes the following members.
| Name | Description | |
|---|---|---|
  | DisableEvents | Disables all events for the specified event source. |
| Dispose | Releases the resources used by the current instance of the EventListener class. |
| EnableEvents(EventSource, EventLevel) | Enables events for the specified event source that has the specified verbosity level or lower. |
| EnableEvents(EventSource, EventLevel, EventKeywords) | Enables events for the specified event source that has the specified verbosity level or lower, and matching keyword flags. |
| EnableEvents(EventSource, EventLevel, EventKeywords, IDictionary<String, String>) | Enables events for the specified event source that has the specified verbosity level or lower, matching event keyword flag, and matching arguments. |
| Equals(Object) | Determines whether the specified object is equal to the current object. (Inherited from Object.) |
  | EventSourceIndex | Gets a small non-negative number that represents the specified event source. |
| Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
| GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
| GetType | Gets the Type of the current instance. (Inherited from Object.) |
| MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
| OnEventSourceCreated | Called for all existing event sources when the event listener is created and when a new event source is attached to the listener. |
| OnEventWritten | Called whenever an event has been written by an event source for which the event listener has enabled events. |
| ToString | Returns a string that represents the current object. (Inherited from Object.) |
An event listener represents the target for all events generated by event source (EventSource object) implementations in the current application domain. When a new event listener is created, it is logically attached to all event sources in that application domain.
 Note |
|---|
You must explicitly call the Dispose method on the EventListener object when a listener is no longer needed. |
An event listener can enable or disable on a per-current event source basis by using event levels (EventLevel) and event keywords (EventKeywords) to further restrict the set of events to be sent to the listener. The listener can also send arbitrary commands to a specific current event source by using the SendCommand method. The meanings of the commands are specific to the implementation of the event source.
If the Guid property in the EventSource object that is used to enable or disable events is Empty, all event sources in the application domain are affected.
Multiple event listeners can be defined in a single application domain. Each listener is logically independent of the other listeners so that events that are enabled or disabled by one listener affect only that listener. It is possible for commands sent with the SendCommand method to do a semantic operation (such as a garbage collection or flushing data) that affects the other listeners, but this is the exception rather than the rule.
Each event source keeps a list of event listeners that it sends events to. A set of filtering criteria is associated with each event source-listener pair. These criteria determine the events that listener will receive for the current event source. Listeners receive the events on their OnEventWritten method. Therefore, subclasses of EventListener must override this method to do something useful with the data.
When a new event source is created, the OnEventSourceCreated method is called. Every current event source gets exactly one OnEventSourceCreated call for every current event source that can send it log messages. When an event listener is created, a series of OnEventSourceCreated calls are made to notify the new listener of all the event sources that existed before the listener was created.
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
