JSON IList Covariance

An Unexpected Roadblock I ran into a an unexpected roadblock the other day when refactoring code that controls JSON de-serialization. It forced me to read up on the dreaded topic of covariance and contravariance in C#. During code review, I was asked to change the technique I used to specify how JSON should be de-serialized into a root type that includes properties typed as interfaces. The conundrum is what classes should be instantiated for these properties? I solved this problem using Json.NET JsonSerializerSettings.TypeNameHandling. This embeds type names into JSON text as properties named “$type”. When the JSON text is de-serialized, […]

The Web Protocol Is the Integration

Last week I had a frustrating debugging session with an integration partner. They provide financial services we’re integrating into our website. They provide these services via a JSON web service endpoint. The Project I have architected a server-to-server solution that enables our server to post and retrieve data to / from their service. This is secured using TLS and JWT. While some integration features are implemented using a client-to-server architecture (and a separate JWT because it’s revealed to the client), the majority of integration features are implemented using a server-to-server architecture with a private JWT. Server-to-Server. Remember that- it’s important […]

Complex Object Graphs, Side Effects, and the Record Pattern

I hope you and your loved ones are doing as well as can be expected in these difficult times. I feel very fortunate to be gainfully employed during the Coronavirus pandemic. Introduction I ran into an interesting coding issue at work I’d like to discuss here. It involves a subtle object reference inequality bug in my implementation of the Record Pattern. At least that’s what we call the pattern at work. To discuss the issue here I’ll change the names of classes to avoid revealing any intellectual property and simplify the code to the minimum necessary to demonstrate the issue […]

Leaderless Replication

Introduction I have been reading Designing Data-Intensive Applications by Martin Kleppmann. (I heard of the book via a review Henrik Warne posted on his blog. I encourage you to read Henrik’s blog- excellent content, clearly articulated). I am only a third of the way through the book but can already say it is one of the best technical computer books I have ever read. As I said in a comment I left on Henrik’s blog, Martin Kleppmann has put a lot of effort into writing clearly and without pretension. He doesn’t use terms without defining the concepts behind them. And […]

Extending Dapper’s ORM Multi-Mapping Capabilities

Since I last posted, my wife and I have bought a new home, moved, sold our previous home, and ran the Chicago marathon. All while getting up the learning curve and taking on more responsibility at our new jobs (both started in June). Needless to say, I’ve had no time for tech blogging. Until now. OK, let’s get to it: Dapper is a great micro-ORM library. It’s simple and highly performant. I love its Multi-Mapping feature, which simplifies mapping columns from a SQL result set into multiple object types. It has an annoyance though: The lambda method provided by the […]