Notes on software and the ideas behind it

Find the meaning
behind the code.

I’m Fred Yang. I write about software—how it works, why it behaves the way it does, and the ideas that make code easier to reason about.

Open the notebook

Working notes / 2026

Recently mapped

Architecture, reactivity, and the hidden relationships that shape frontend systems.

asp.net mvc

View is the king.

ASP.NET MVC is very hot today, it catches more and more attention from asp.net developer. There are many problems it tries to solve, like testability, separation of concern ect. But to me the most...
Follow the thread
WF

EventHandlingScopeActivity

The EventHandlingScopeActivity is a dramatically different type of event handling activity. It has two discrete sections: a main line child activity and a set of event handling activities. The single main line child activity...
Follow the thread
WF

Manually controlling correlation

<p> In the previous examples, you’ve seen that as local service events are raised, they are routed to the correct workflow instance. The magic that accomplishes this is the workflow instance ID that is...
Follow the thread
field note

Using HandleExternalEventActivity

<p> Implement the class that will be used as the vent arguements,this argument must derived from ExternalDataEventArgs. </p> <p> Define the evetn in a local service interface. A local service interface is one that...
Follow the thread
WF

Event-Driven Activities

<p> WF includes a group of activites that work together to provide event handling within workflow. Some of these activites wait for an external event(eg HandleExternalEventActivity), while others trigger and handle an event internally(...
Follow the thread