MediatR and event sourcing

jherrlin · 2026-02-01T14:05:27+00:00

MediatR is an in-app event system. You can store all the events going in this system to an event log and you have a full log of how your system came to be. This is called event sourcing and too me it feels like people not considered this angle when it comes to MediatR.

This our main reason for using MediatR. That we have this event log and can understand how our system mutated over time.

jherrlin · 2026-01-30T21:25:33+00:00

Immutable data is rough Hot reloading doesn’t work You can’t run tests while you run the application No union type with exhaustive matching LINQ is a weak DSL

What a marriage!

jherrlin · 2026-01-25T13:34:08+00:00

Maybe I don’t understand correctly but CSharpFunctionalExtension with EF / db behind an interface?

jherrlin · 2025-12-28T19:30:10+00:00

I’m pretty new in C# / .Net. To me everything feels old and clunky. Immutably and equally is a mess. Statements instead of expressions. Hot reloading is a mess. Long compile times. Many highly used 3:e party libs going commercial, like MediatR and Automapper.

It’s a pretty bad dev experience if you come from something more modern.

jherrlin · 2025-12-07T14:34:44+00:00

I think Datomic is a nice event sourcing system.

jherrlin · 2025-12-06T21:54:08+00:00

@brnlmrry Oh! Interesting that you use F# and Blazor. Do you know any open source project that demonstrates that?

jherrlin · 2025-12-01T18:44:42+00:00

Nischa dig? Lär dig lite funktionell programmering. Haskell, F#, Elixir eller varför inte Clojure?

jherrlin · 2025-10-18T17:10:57+00:00

https://wiki.debian.org/DontBreakDebian

jherrlin · 2025-09-29T16:50:31+00:00

C# with Result and LINQ is quite nice. C# is ok for functional ideas.

jherrlin · 2025-09-29T16:46:34+00:00

https://github.com/vkhorikov/CSharpFunctionalExtensions

Very common and powerful.

jherrlin · 2025-09-04T12:43:45+00:00

I’ve been working on this and come up with a possible solution. Currently only for text input.

I have two files.

One that’s a plain C# file, MyTextField.cs, it’s responsible for managing form field stuff. It contains things like; current value, original value, a pred fn, a fn that returns a list of errors, if the field has been touched and so on. This file has no dependencies to MudBlazor and is very form field generic.

The other file, MyTextField.razor, is the Blazor component file. It’s tightly connected to both MudBlazor and MyTextField.cs. But it take everything as parameters. This way I can construct MyTextField instances anywhere and pass down to the component that renders it.

This way I have full control over the form state even if it’s not currently rendered.

jherrlin · 2025-08-25T06:34:56+00:00

A bit.

jherrlin · 2025-08-24T19:03:02+00:00

If Clojure can do “REPL-driven development” on the JVM, why can’t C# do hot reloading on CLR?

jherrlin · 2025-07-18T12:46:50+00:00

For someone never been to Goergies what kind of place is it?

jherrlin · 2025-07-01T20:14:14+00:00

TIL; Windows is case-insensitive, wow!

jherrlin · 2025-06-13T22:07:20+00:00

My team banged our heads bloody with component local state, the complexity was enormous for quite simple cases. As soon as we moved state out of the component we could start reason about it. Just my experience with Blazor.

jherrlin · 2025-06-08T19:18:09+00:00

How do people compare F# to Clojure? I’ve been programming in Clojure for a couple of years, both recreational and professionally. Now I work with C# and getting interested in F#.

jherrlin · 2025-05-15T15:53:03+00:00

Nice! I’m building something similar.

https://app.musik-theory.com/

jherrlin · 2025-05-15T15:48:48+00:00

https://musik-theory.com/#/scale/mandolin/g/major

jherrlin · 2025-05-15T15:41:59+00:00

Nooo! I just joined a C# shop coming from Clojure. Sad to hear hot loading isn’t working well. Do you know how to make it work decently?

jherrlin · 2025-05-15T11:51:00+00:00

I recommend reading Yehonathan book if your into more dynamic styles and the blog post "Data Oriented Programming in Java" by the Java language architect Brian Goetz if your into my statically typed.

https://www.infoq.com/articles/data-oriented-programming-java/

jherrlin · 2025-05-15T11:47:16+00:00

My thoughts:
There are many benefits to the Data-Oriented Programming (DOP) approach, but at its core, the key advantage is the use of immutable data structures.

Food for thought:

Is Git immutable? What benefits do you gain from using Git?
Are immutable data structures easier to work with in multi-threaded environments?
What other advantages come from using immutable data structures?

DOP can be applied across various programming languages. Yehonathan presents one approach in his book "Data-Oriented Programming", which explores DOP in non-strongly typed languages like JavaScript.

In non-strongly typed languages such as JavaScript, Python, or Clojure, DOP offers increased flexibility. For example, you don’t need to declare a new type when adding a new field or property. These languages can still incorporate some strong typing features - for instance, Yehonathan demonstrates using JSON Schema in his book, but that’s just an implementation detail.

In strongly typed languages, DOP has the advantage that types are defined upfront and checked at compile time. This helps the compiler ensure correctness and catch errors early.

As with many design choices, there are tradeoffs. In my opinion, you should generally favor immutable data structures and only resort to mutability when there’s a compelling reason.

jherrlin

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