Development with a Dot

Introduction LINQ extension methods are pretty cool and they make our lives much easier. They are implemented as .NET extension methods over the Enumerable class in the System.Linq namespace and as usual they all apply to IEnumerable<T> sequences. This time I'll be talking about some LINQ methods that are not so commonly used (as per my understanding). Not sure about you guys, but sometimes I don't even remember that some of these exist. Aggregate/AggregateBy Aggregate applies an accumulator function over a sequence, reducing it to a single value. AggregateBy (.NET 9+) does the same but groups by a key first, producing one accumulated result per key. // Aggregate var product = new[] { 1, 2, 3, 4 }.Aggregate((acc, x) => acc * x); // 24 // AggregateBy var words = new[] { "apple", "ant", "bear", "bee" }; var lengthSums = words.AggregateBy( keySelector: w => w[0], seed: 0, func: (acc, w) => acc + w.Length...

It was with great honour and sense of privilege that I received that email this Wednesday: I had been renewed as Microsoft Most Valuable Professional (MVP) again, for the period 2026-27! It is the third time in a row, and the 8th (I had previously been awarded from 2014-15 and until 2019. It is really a great privilege to be part of such a fantastic family, and I guess it's a recognition for something I did well - at least, so I hope! During the years I met many fellow MVPs, some of which became my friends, and I had a great time in Redmond, Bellevue, Seattle, Madrid, Rome, and Lisbon. It is a pity to see many of them gone from the programme, but there are new people, which is absolutely normal. I was actually away too for some years, until I was recommended by  Erik Ejlskov Jensen a couple years ago. I met lots of people from Microsoft, took part in 3 MVP Summits , attended many technical sessions,  and numerous Program Group Interactions and mailing list discussions. What I...

Introduction When using AWS  for development, sometimes it is useful to have some sort of emulator, so that we don't incur in costs while doing development and debugging. For that, we have local cloud emulators, and LocalStack used to be the standard one not too long ago; the problem is, its licence changed and it is now generally not free. The good news is that there are alternatives that are free, such as MiniStack (GitHub:  MiniStack ), a free and open-source AWS cloud emulator that can emulate more than 55 AWS services and that is very similar to LocalStack. On this post I'll be talking about how to set it up so that we can point to it and use it as if it were the real thing with .NET. We will be using Docker Compose to spin up the local environment. Docker Compose We want to use the latest MiniStack image, which is made available from https://hub.docker.com/r/ministackorg/ministack . Our docker-compose.yml file will look like this: services: ministack: image: m...

Introduction C# records and record structs  are relatively new. Records offer some advantages over regular classes and structs, which I will cover here, but they are essentially another way to declare them. This is another back to basics article. We essentially use records for: Entities, such as the ones we would store in a database Value objects/ Data Transfer Objects Immutable classes Let's now see how to work with them. Syntax Records are declared like this: public record Point(int X, int Y); Or like this, with the exact same meaning: public record Point { public int X { get; init; } public int Y { get; init; } } And we instantiate a record just like any other class or struct: Point p1 = new(1, 2); //or var p1 = new Point(1, 2); We can, of course, use  positional or named arguments : var p1 = new Point(Y: 2, X: 1); It is possible to add new properties (or methods) besides the ones declared on the primary constructor , we don't need to live with just those pro...

Introduction Some of you may remember - and hopefully have even tried! - my Isolator project . Isolator is a framework for running isolated code for .NET. What this means is that possibly unsafe code can be run in a secure, isolated, way. It offers some quite different isolation strategies: Process isolation : the code to execute runs in another process, possibly under a different identity (on Windows only) Assembly isolation : uses an assembly load context to isolate the code execution, which is then unloaded Distributed isolation : the code to execute is sent to possibly another server for execution Scanned : the code to execute is first checked for problematic code using my ReferencesScanner project Now, I added support for Docker isolation! What this means is, if you have Docker running on your machine, you can spawn an image that will just be used for running your code, and after that will be gone. This provides another very restricted level of isolation. For Docker A...

Introduction This post picks up where this one left. It will be my second post on using LLMs, and AI, in general. This time I'm going to cover integrating MCP tools with the LLM's response. MCP stands for Model Context Protocol , and it is an open standard . In a nutshell, it is a protocol designed to help LLMs communicating with the real world, for example, accessing a database, getting real-time weather information for a specific location, creating a ticket in some system, sending out an email, etc. We need an MCP host and some tools registered with it. There are many ways by which LLMs can communicate with the MCP host, always using JSON-RPC 2.0 for messaging: Standard input/output, if running on the same machine HTTP calls Streams, mainly for the same machine Custom-defined Now, I won't go through all of them now, I'll just pick HTTP transport, as it's probably the most usual one. Also, I will be using the  OpenAI  API. Essentially, we registe...

I started posting on Medium about my PhD adventure. Nothing much, for the time being, but you are more than welcome to check it out:  https://medium.com/@rjperes75 . I plan to write a bit more about what I'm doing, how I got here, and what challenges/accomplishments I encounter along the way. Always for free, of course! ;-) Posts so far: My PhD adventure — Part I My PhD adventure — Part II

Introduction This will be the first post on AI that I write, which is really a shame, as it's such an interesting and vast topic; you should expect more in the future! This time I'm going to talk about code generation from inside .NET using OpenAI  and it's Azure integration , in a structured way. As you know, code generation is one of the typical usages for Large Language Models (LLMs); it is part of what is called generative AI . It essentially works out of the box, but we can tweak it to be more useful. In this post I’ll show how we can get multiple files in response to a prompt. We will use Azure, but all the concepts are really from OpenAI. Let's start from the beginning. Setting Up OpenAI in Azure From the Azure portal , start by creating a new resource of type Microsoft Foundry  (it supports OpenAI  and others): QIf you need more info on this operation, please have a look here . You can now see it in the dashboard page: The end...

Introduction Note: some people complained that what I actually called Dependency Injection is actually Inversion of Control. I won’t get into that fight, to me, Dependency Injection is a form of Inversion of Control. The  Strategy Pattern  (sometimes known as Policy) originated in the seminal book Design Patterns , by the Gang of Four. It is a behavioural design pattern  that allows picking a specific strategy at runtime. The concrete strategy to use can change dramatically how the application behaves. Quoting: instead of implementing a single algorithm directly, code receives runtime instructions as to which in a family of algorithms to use. Dependency Injection (DI), also known as Inversion of Control (IoC) - they’re not quite the same, but, for the purpose of this post, we can think of them as the same, even though this raises heated discussions - is built-in in .NET Core (now, .NET) since the start, and whilst we generally return the same implementation type ...

Introduction We all know  EF Core Migrations . They have been around for quite some time, some people like them, others prefer alternatives (hello, Flyway , DbUp , FluentMigrator !). I'm not going to discuss that, but, instead, how to seed data to a database, either using EF Core migrations or not. This is, of course, for inserting initial/reference data that must always be present, for Microsoft's opinion on this, please see this page . This post assumes that you know about migrations - how to create and apply them, at least, and that you have all it takes for it, including  EF Core Tools  and the  Microsoft.EntityFrameworkCore.Design  NuGet package. Migrations and the creation methods ( EnsureCreated , EnsureCreatedAsync ) are mutually exclusive , so you need to pick one, depending on your strategy. For actually adding data, we have essentially four options: Explicit insertions Data-only migrations Entity configuration Context configuration (explicit seeding)...