This article is the third in a series on covariance and contravariance: Covariance in arraysContravariance in interfacesCovariance in interfaces In the previous article I showed how an interface could be contravariant, meaning it is expecting a smaller type for something you pass it. In this article I will show how an interface can be covariant, … Continue reading Covariance and contravariance, part 3: Covariance in interfaces
Category: C#
Captured variables
This article is about captured variables in C#. In case you've not come across them before, they're where some code appears to capture and drag with it a variable declared outside the code, such that the code can continue using the variable long after it appears that this should be possible. They’re not something I … Continue reading Captured variables
Covariance and contravariance, part 2: Contravariance in interfaces
This is part two in a series about variance – contravariance and covariance. Arrays and listsContravariance in interfacesCovariance in interfaces In the previous article I introduced the concepts of variance and type size. I also gave arrays as an example of covariance. In this article I’ll give an example of contravariance, and go into more … Continue reading Covariance and contravariance, part 2: Contravariance in interfaces
Covariance and contravariance – part 1: Arrays and lists
This post is the first in a series - for once I will split a large topic into a few small posts. The series is about covariance and contravariance, together known as variance. Arrays and listsContravariance in interfacesCovariance in interfaces Covariance and contravariance are terms I came across occasionally, and never understood properly. Having put … Continue reading Covariance and contravariance – part 1: Arrays and lists
Usability for programmers
I recently started learning Xamarin. I should say I’ve started learning it again, because the first time I just couldn’t get into it. This time it’s going better, although I’ve still been struck by something that’s surprisingly labour-intensive and so surprisingly annoying. This made me think about the relatively cushy world I normally experience when … Continue reading Usability for programmers
Explaining virtual methods in C# with words and pictures
In this post I will try to explain virtual methods in C#. There are similar concepts in other languages, like C++ and Java, but I can’t vouch that all the details I go into here will apply exactly to any other language. The whole post is quite long, but I want to get to a … Continue reading Explaining virtual methods in C# with words and pictures
Performance optimisation – for machines or people?
I recently watched a video and listened to a podcast that form an interesting pair of opinions about performance. The video is Patterns for high-performance C# and the podcast is SE-Radio Episode 357: Adam Barr on Software Quality. There are two things where the podcast and video have no differences: the system must behave correctly, … Continue reading Performance optimisation – for machines or people?
Unit testing database queries
In this post I will try to describe an approach to unit testing database queries. It happened to be inspired by some testing I was doing of some C# code, but you could apply the same ideas to other languages. Note that if you’re unit testing stored procedures then I recommend using something like tSQLt, … Continue reading Unit testing database queries
Lazy initialisation and threads (in C#)
Lazy initialisation is a way to set up everything needed to initialise something, but put off the initialising until later, usually when the value of the thing-being-initialised is needed for the first time. You might want to use lazy initialisation because something is expensive to initialise, and you might not need it. Or because you … Continue reading Lazy initialisation and threads (in C#)
Documenting ASP.NET REST APIs with Swagger / Swashbuckle
Introduction Swagger is a way to document a REST API, and tools can automate much of this process (but not all of it). At the centre of things is a JSON file that describes the API. You can create this file by hand or use a tool to generate e.g. from the API source code. … Continue reading Documenting ASP.NET REST APIs with Swagger / Swashbuckle
