TinyCQRS is a truly tiny library that supports the much venerated CQRS pattern
See the TestApp project but a simple example would be something like:
var plugin = new HelloWorldPlugin();
// a basic hello world command, register a user ID with a name
var command = new HelloWorldCommand { UserId = 1, Name = "steve" }
var result = plugin.Handle(command);
// query to retrieve the name
var query = new HelloWorldQuery { UserId = 1 }
var queryResult = plugin.Handle<HelloWorldQuery>(query);
// result: steve