Click here for step by step implementation of the CQRS MediatR design pattern. In this article, we are going to do request logging into an Asp.Net application Core application build on the CQRS MediatR design pattern. The application request logging helps to track the time taken per request. The MediatR provides a pipeline interface that is 'IPipelineBehavior' that helps to implement our logging logic. IPipelineBehavior: The 'IPipelineBehavior' exactly works like Asp.Net Core middleware, but its starting execution and ending execution happens within the 'IMediator'. So the 'IMediator.send()' is usually used to invoke the 'Query' or 'Command' handlers. So if we implement 'IPipelineBehavior' then begin logic inside of its start executes then invokes 'Query' or 'Command' handlers, later again go through 'IPipelineBehavior' and executes the end logic. Create A .Net5 Web API Sample Application: In this