Ask a room of developers what C# is for and the answers arrive fast: ASP.NET backends, corporate line-of-business software, something that runs on a Windows server in a building with a badge reader at the door. That picture is accurate and dramatically incomplete. The same language scripts the mobile game that passed 500 million downloads in roughly two months, ships airline and restaurant apps to tens of millions of phones, and is one of the languages behind the IDE that millions of developers open before their first coffee.

Softwarium is a software engineering and IT staff augmentation company supporting software product companies and technology teams — building C# and .NET products from cross-platform mobile applications to security-critical enterprise features such as the Secret Server mobile autofill delivered for Thycotic, now Delinea. 

Below are seven examples of products built with C# that most developers, C# developers included, would not predict. Some are single applications; some are app portfolios sharing one C# foundation. Each section starts with the surprise and then shows the evidence behind it. 

In July 2016 the world went outside. Pokémon GO passed 500 million cumulative downloads within roughly two months of launch, according to The Pokémon Company’s press release of September 2016, and in 2019 The Pokémon Company announced one billion cumulative downloads. Those figures count downloads, reinstalls included, and say nothing about unique players; the launch-window record stands on its own.

Under all of that sits Unity, and C# is Unity’s supported scripting language for gameplay and application logic. Niantic engineers presented the game’s Unity architecture on stage at Unite 2016, and Niantic’s job postings for Pokémon GO engineering roles list Unity and C# as requirements. Much of the client-side gameplay and interaction logic, the catch mechanics, the map, the AR overlay, was built in Unity using C#.

One precision worth keeping. The confirmed C# layer is the game client; Niantic’s backend uses other technologies, and this post claims nothing about it. The point stands on the client alone: the game that introduced augmented reality to hundreds of millions of people runs C# scripts inside a game engine.

Among Us is the better story for anyone who has ever shipped with a tiny team. Innersloth, a three-person studio, watched the game sit at roughly 30 active players in May 2020. By October 2020 it had reached 60 million peak daily active users, and Unity’s official case study reports more than 500 million players.

The stack is Unity with C# scripting. Innersloth’s own team page lists “Unity Programmers” as the engineering role, which tells you where the game logic lives. Mobile, PC, Nintendo Switch, PlayStation: one shared Unity project and shared C# game logic across all of them, with platform-specific integration work on top.

The most useful lesson here is how ordinary the tools were. Nothing Innersloth used is exotic or proprietary; the same engine and the same language are available to any three-person team with an idea and a lot of patience. The phenomenon was the game. The technology was off the shelf.

The tool you use to write C# is built with C#. Visual Studio, the full IDE, is developed using C# and C++, among other technologies. GitHub’s Visual Studio topic page states it plainly (“Visual Studio is made with C# and C++”), and Visual Studio appears on Microsoft’s own .NET customer showcase as a .NET application, alongside the companies running .NET in production. Solution loading, IntelliSense, debugging, profiling, for millions of developers, on the language it hosts. This is the meta example of the list.

Now the distinction that trips up half the internet. Visual Studio and Visual Studio Code share a brand and nothing else. VS Code is a separate product and a separate codebase, written in TypeScript and JavaScript on Electron. Any article telling you VS Code is written in C# is wrong, and it pays to know which product is under discussion before the next architecture meeting. The C# claim belongs to Visual Studio, the full IDE, and to nothing else that carries the name.

Booking, check-in, boarding passes, flight status: Alaska Airlines built its passenger apps for iOS, Android, and Windows with Xamarin, Microsoft’s cross-platform framework for C#. The scale figure comes from the same page as the technology claim. At the time of the case study, Microsoft’s Xamarin customer showcase reported that Alaska Airlines served more than 17 million customers a year across a route network spanning 60 cities.

The engineering decision is the reason the example belongs on this list. Three platforms normally means three teams, three release cycles, and three sets of bugs that look similar and are not. Xamarin let one C# team share the business logic across platforms and ship a native app on each, with the platform-specific UI layers written on top of the shared core.

A note on the framework, once. Microsoft’s recommended successor for new .NET cross-platform app development is .NET MAUI. The apps described in this post were built with Xamarin at the time, and the shared-C# approach continues in MAUI.

Nobody expects a recipe app to be a C# showcase. BBC Good Food rebuilt its iOS, Android, and UWP apps with Xamarin and C#, and Microsoft’s Xamarin customer showcase reported that all three launched from a single shared codebase.

The instructive detail is the motive. A media brand’s engineering team is small relative to its audience, and the audience cooks on every device it owns. Shared C# code let one team reach all of them without maintaining three parallel products. C# was the tool that made the arithmetic work, and the home cooks scrolling for a weeknight curry never had to know.

Order a Wingstop delivery, a Five Guys pickup, or an Applebee’s table through the brand’s own app and there is a fair chance you are inside C#. Olo builds custom-branded ordering apps for restaurant chains, and at the time of the case study Microsoft’s Xamarin customer showcase reported more than 150 restaurant brands, including those three, and over 30 million users, with the apps built on Xamarin and C#.

Olo’s case is C# at horizontal scale. Alaska Airlines demonstrates shared code across three platforms; Olo demonstrates shared code customized per brand across dozens of distinct consumer apps, each with its own logo, menu, and loyalty rules. One engineering team maintaining one product that appears to the market as a hundred and fifty.

The last example is the one Softwarium can vouch for from inside the project. Secret Server, from Thycotic (now Delinea), is a privileged access management platform; Delinea’s own documentation describes it as installed as an ASP.NET website on IIS, which places it squarely in the .NET world this post is about. Softwarium’s published case study records the client’s statement that its tools serve over 10,000 organizations, from small businesses to the Fortune 100.

Softwarium built the Secret Server mobile autofill credentials feature: automatic population of login and password fields in other mobile apps and in mobile browsers, with the user confirming through Face ID, Touch ID, or PIN before the credentials fill. The design objective was to combine the convenience of autofill with device-level authentication, so that a privileged credential never fills without the account holder present.

Scope, stated exactly: mobile autofill and biometric authentication for Secret Server Mobile, delivered for a .NET-based PAM platform. That is the work Softwarium documented, and that is the claim.

Seven examples, one thread. C# scripts the game clients of Pokémon GO and Among Us, forms the shared code beneath the Alaska Airlines, BBC Good Food, and Olo apps, is one of the languages Visual Studio is built with, and underpins the .NET platform whose mobile autofill Softwarium delivered for Secret Server. Game scripting, cross-platform mobile, IDE engineering, enterprise security software: the language covers all four, and this list only holds the surprises. For the enterprise platforms C# is usually credited with, see the companion post on real-world applications built with .NET and Azure.