Components

Components are the data containers in the ECS world and should only contain some properties to contain data, there should be no logic in components, if there is logic then you are probably a bad man and need to step away from the computer.

Using components

You will need to make your own implementations of IComponent which encapsulate the data your components need to expose to the systems. It is fairly simple really just implement IComponent and it just does its stuff.

Composition

So the whole point behind components are that they can contain anything, so if you need to contain complex data it would make sense to go write a c# POCO somewhere to encapsulate your data then just include that via composition inside your component.