I implement Event Sourcing and CQRS pattern in my application. I inspired by CQRS journey where I downloaded sample code. There I found whole infrastructure for Event sourcing (
The general recommendation is to not write your own event store. Sure, you can write your own ES, but do it only for educational purposes. For production systems I would recommend you to use an existing ES. It might look like a lot of unnecessary infrastructure code at first but you will soon notice that you do need it. In its simplest form ES is not that hard but once you start dealing with concurrency, performance etc it will be more complicated.
NEventStore and Event Store are two well known event stores.
As a side note from my own experience, do not underestimate the time that you will need to invest on infrastructure code even if you use an existing ES.