Many files contain code for a single namespace. Starting in C# 10, you can include a namespace as a statement, followed by a semi-colon and without the curly brackets:

namespace MyCompany.MyNamespace;

class MyClass     // Note: no indentation
{
   ...
} 

This simplifies the code and removes a level of nesting. Only one file-scoped namespace declaration is allowed, and it must come before any types are declared.