Represents the method that will handle a BeginRequest event, which occurs as the first event in the HTTP integrated request-processing pipeline for the current request.
When a request-level module is registered for the RQ_BEGIN_REQUEST event notification, IIS will call the module's OnBeginRequest method when a request enters the integrated request-processing pipeline.
Request-level modules can register for the BeginRequest event notification by registering for RQ_BEGIN_REQUEST in the module's RegisterModule function.
IIS calls a module's OnBeginRequest method before authentication and authorization; this allows developers to use the OnBeginRequest method to process requests where the client's identity is not an issue.
Not all requests enter the integrated request-processing pipeline. A request for an image file that can be satisfied from the cache will not enter the integrated request-processing pipeline; therefore, the OnBeginRequest method will not be called.
The following example demonstrates how to create a request-level HTTP module that registers for the RQ_BEGIN_REQUEST event and post-event notifications. When a request enters the pipeline, IIS will call the example module's OnBeginRequest and OnPostBeginRequest methods. Each method will write an entry in the application log of the Windows Event Viewer. When processing is complete, the module will exit.