EventLog.WriteEntry Method (String, EventLogEntryType, Int32, Int16)
Assembly: System (in system.dll)
public void WriteEntry ( string message, EventLogEntryType type, int eventID, short category )
public void WriteEntry ( String message, EventLogEntryType type, int eventID, short category )
public function WriteEntry ( message : String, type : EventLogEntryType, eventID : int, category : short )
The string to write to the event log.
One of the EventLogEntryType values.
The application-specific identifier for the event.
The application-specific subcategory associated with the message.
The method attempted to register a new event source, but the computer name in MachineName is not valid.
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The source is already registered for a different event log.
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eventID is less than zero or greater than UInt16.MaxValue.
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The message string is longer than 32766 bytes.
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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 category to the event log. The Event Viewer uses the category to filter events written by an event source. The Event Viewer can display the category as a numeric value, or it can use the category as a resource identifier to display a localized category string.
The category parameter should be a positive value. Negative category values appear as a complementary positive number in the Event Viewer. For example, a –10 appears as 65,526, a –1 as 65,535.
To display localized category strings in the Event Viewer, you must use an event source configured with a category resource file, and set the category to a resource identifier in the category resource file. If the event source does not have a configured category resource file, or the specified category does not index a string in the category resource file, then the Event Viewer displays the numeric category value for that entry. Configure the category resource file, along with the number of category strings in the resource file, using the EventLogInstaller or the EventSourceCreationData class.
In addition to the category, you can specify an event identifier for the event being written to the event log. Event identifiers, along with the event source, uniquely identify an event. Each application can define its own numbered events and the description strings to which they map. Event viewers display these string values to help the user understand what went wrong and suggest what actions to take.
Finally, you can 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 set the Source property on your EventLog component before you can write entries to the log. 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.
If the source specified in the Source property of this EventLog instance is not registered on the computer that your component is writing to, WriteEntry calls CreateEventSource and registers the source.
If you do not specify a MachineName for your EventLog instance before you call CreateEventSource or WriteEntry, the local computer (".") is assumed.
If the system needs to register the Source through a call to WriteEntry and the Log property has not been set on your EventLog instance, the log defaults to the Application log.
Many exceptions listed above are generated by errors raised during the process of registering the 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 you write an entry to a remote computer, the value of the message (the text string) might not be what you expect if the remote computer is not running the .NET Framework.
If the message parameter contains a NUL character, the message in the event log is terminated at the NUL character.
// Create an EventLog instance and assign its source. EventLog myLog = new EventLog(); myLog.Source = "ThirdSource"; // Write an informational entry to the event log. Console.WriteLine("Write from third source "); myLog.WriteEntry("Writing warning to event log.", EventLogEntryType.Warning, myEventID, myCategory);
// Create an EventLog instance and assign its source. EventLog myLog = new EventLog(); myLog.set_Source("ThirdSource"); // Write an informational entry to the event log. Console.WriteLine("Write from third source "); myLog.WriteEntry("Writing warning to event log.", EventLogEntryType.Warning, myEventID, myCategory);