A crash course in C# and .NET 10 for a TypeScript developer with zero C# experience. It starts from the basics, reading a whole C# program, methods, properties, collections, mapped one to one to the Node and Nest you already know, with exercises and quizzes throughout. Then it teaches the real easyJet Fusion idiom (the Result pattern, value objects, SmartEnums, DDD layers, EF Core migrations, the xUnit stack, the build gate), and finishes by decoding the actual .NET review comments Rai has received so you understand what your reviewers meant. Each concept comes with the 'from TS you'd do X, in C#/Fusion you do Y' mapping. Finish able to ship a Fusion PR nobody calls slop, and to read your own reviews fluently.
Take a piece of C# a TS developer would write by instinct: a class with a public constructor and no validation, a string literal where an enum belongs, a .Result blocking call, a repository that mixes reads and writes, and a test that only checks the happy path. Refactor it end to end to the Fusion bar: a value object with a private constructor and a Create factory returning Result<T>, a SmartEnum instead of the string, async/await with a CancellationToken threaded through, a clean CQRS split, an endpoint that branches on the Result type, and an xUnit + Shouldly test that covers a boundary case. Then make it survive the gate: dotnet build, dotnet format --verify-no-changes, and the analyzers, all green. When that whole loop is muscle memory, your PRs stop reading as a TS developer guessing at C# and start reading as someone on the team.