Introduced in C# 10.0, file-scoped namespaces simplify the common pattern of having a single namespace per file. Instead of wrapping the entire file content in a namespace block, you declare the namespace once at the top with namespace MyNamespace; and it applies to all code in that file. This reduces nesting and improves readability.
Why it matters
File-scoped namespaces eliminate one level of indentation and make files easier to scan. Since most C# files contain exactly one namespace, this feature reduces boilerplate significantly. The cleaner structure improves code readability and is now the recommended pattern for most new C# projects.
Cautions
File-scoped namespaces only work when there is a single namespace per file. If you need multiple namespaces in one file (an uncommon but valid pattern), you must use traditional block-scoped namespaces. Additionally, file-scoped namespaces cannot be mixed with block-scoped namespaces in the same file, which may require refactoring legacy code.
Using file-scoped namespaces
File-scoped namespaces eliminate indentation and reduce nesting, applying the namespace to the entire file with a single declaration.
Valid since C# 10.0
// UserService.cs - using file-scoped namespace (C# 10.0)
namespace MyApp.Services;
public class UserService
{
public void PrintUser(string name)
{
Console.WriteLine($"User: {name}");
}
}
// Logger class in the same file-scoped namespace
public class Logger
{
public void Log(string message)
{
Console.WriteLine($"[LOG] {message}");
}
}Comparison with traditional namespaces
See how file-scoped namespaces simplify code structure compared to traditional block-scoped namespaces.
Valid since C# 10.0
// TRADITIONAL BLOCK-SCOPED NAMESPACE (pre-C# 10.0)
/*
namespace MyApp.Services
{
public class UserService
{
public void PrintUser(string name)
{
Console.WriteLine($"User: {name}");
}
}
}
*/
// FILE-SCOPED NAMESPACE (C# 10.0+)
namespace MyApp.Services;
public class UserService
{
public void PrintUser(string name)
{
Console.WriteLine($"User: {name}");
}
}
// Benefits:
// - Cleaner indentation
// - Simpler visual structure
// - Less nesting required
// - Modern, recommended approach