Why I Chose CRTP for My C# Result Pattern Library

I’ve been working on a C# Result Pattern library called REslava.Result—zero dependencies, functional, and designed for fluent APIs. But I kept hitting a wall: type information loss in method chains.

csharp
CopyError error = new Error("Something went wrong")
    .WithMessage("Updated message")  // Returns Reason, not Error
    .WithTag("Code", 404);           // Can't call Error-specific methods

Then I discovered CRTP (Curiously Recurring Template Pattern). It’s not magic—just smart C#—and it preserved the derived type through the entire chain:

csharp
CopyError error = new Error("Something went wrong")
    .WithMessage("Updated message")  // Still returns Error
    .WithTag("Code", 404)           // Type-safe and fluent
    .WithTag("Field", "Email");

This solved the core problem: type safety and developer experience in fluent APIs.

I wrote about my journey—how I learned CRTP, generics, functional patterns, and library design—and why this approach beats alternatives.

If you’re into:

• C# advanced patterns
• Functional programming in .NET
• Building reusable libraries
• Or just love solving type puzzles

I’d love to hear your thoughts. What’s your experience with CRTP or Result patterns?

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