LINQ OrderBy – using Comparer<T>.Create and F#’s Object Expressions

Check out my new course Learn you some Lambda best practice for great good! and learn the best practices for performance, cost, security, resilience, observability and scalability.

.Net 4.5 introduced a handy little new method Comparer<T>.Create to aid the creation of bespoke comparers, which is great because it means that you don’t have to define a new Comparer class when it is going to be needed once.

In case you’re wondering, it’s still not possible to define anonymous implementation of interfaces in C#, but with Comparer<T>.Create you can at least create a bespoke instance of IComparer<T> from an anonymous method:

As a side, you can also apply the same technique for other single method interfaces yourself, for instance, if you were happy to ignore the existence of the Zip extension method for the sake of the example, you could define your own Zip extension method which takes in an instance of an IZipper<T, U, V>:

Whilst we’re on the topic of anonymous interface implementation. F# has a nice little feature call Object Expressions, it provides a mechanism for creating anonymous types that are based on existing base type, interface, or set of interfaces, and for the two examples, here’s how that solution might look in F#:

Notice that there’s no need for an explicit implementation class for IZipper<T, U, V> interface at all using Object Expressions and how much less code you end up writing with F#! So seriously, why aren’t you checking out F# already!? Winking smile

Liked this article? Support me on Patreon and get direct help from me via a private Slack channel or 1-2-1 mentoring.
Subscribe to my newsletter


Hi, I’m Yan. I’m an AWS Serverless Hero and the author of Production-Ready Serverless.

I specialise in rapidly transitioning teams to serverless and building production-ready services on AWS.

Are you struggling with serverless or need guidance on best practices? Do you want someone to review your architecture and help you avoid costly mistakes down the line? Whatever the case, I’m here to help.

Hire me.


Check out my new podcast Real-World Serverless where I talk with engineers who are building amazing things with serverless technologies and discuss the real-world use cases and challenges they face. If you’re interested in what people are actually doing with serverless and what it’s really like to be working with serverless day-to-day, then this is the podcast for you.


Check out my new course, Learn you some Lambda best practice for great good! In this course, you will learn best practices for working with AWS Lambda in terms of performance, cost, security, scalability, resilience and observability. We will also cover latest features from re:Invent 2019 such as Provisioned Concurrency and Lambda Destinations. Enrol now and start learning!


Check out my video course, Complete Guide to AWS Step Functions. In this course, we’ll cover everything you need to know to use AWS Step Functions service effectively. There is something for everyone from beginners to more advanced users looking for design patterns and best practices. Enrol now and start learning!


Are you working with Serverless and looking for expert training to level-up your skills? Or are you looking for a solid foundation to start from? Look no further, register for my Production-Ready Serverless workshop to learn how to build production-grade Serverless applications!

Find a workshop near you