Bits of .NET

Helper classes polluting your namespace? File-scoped types are only visible in their file.

Problem:

// HelperClass visible everywhere in project
public class ProductService
{
    // ...
}

public class HelperClass  // Only used by ProductService
{
    // But visible to entire project!
}

Solution – File-Scoped Types:

// ProductService.cs
public class ProductService
{
    private readonly HelperClass _helper = new();
    // ...
}

file class HelperClass  // Only visible in this file!
{
    public void DoSomething() { }
}

// Other files can't see or use HelperClass

Use Cases:
– Private helper classes
– Implementation details
– Test-only classes in test files
– Record types for local use

Works with: class, struct, interface, enum, delegate

Keeps internals truly internal!