This is a short hierarchy summary of the access modifiers in C#.NET, from most restricted to least restricted.

---

private

• Only Accessible within a Class/Struct
• Not inherited by any deriving classes
• Boundaries:
  • Same Assembly: Declared Class

private protected

• Since C# 7.2
• Accessible from within a Class/Struct
• Inherited by any deriving classes
• But only within the current assembly (Project/Namespace)
• Boundaries:
  • Same Assembly: Declared Class
  • Same Assembly: Derived Classes

internal

• (Assembly-Project Priority)
• Accessible from anywhere within the current assembly (Project/Namespace)
• Boundaries:
  • Same Assembly: Declared Class
  • Same Assembly: Derived Classes
  • Same Assembly: Other Classes

protected

• (Class-Inheritance Priority)
• Accessible from within a Class/Struct
• Inherited by any deriving classes
• Boundaries:
  • Same Assembly: Declared Class
  • Same Assembly: Derived Classes
  • Other Assemblies: Derived Classes

protected internal

• (Class-Inheritance + Assembly-Project)
• Accessible from anywhere within the current assembly (Project/Namespace)
• Inherited from any deriving classes
• Boundaries:
  • Same Assembly: Declared Class/Struct
  • Same Assembly: Derived Classes
  • Same Assembly: Other Classes
  • Other Assemblies: Derived Classes

public

• Accessible from everywhere
• Access is not restricted at all
• Boundaries:
  • Same Assembly: Declared Class/Struct
  • Same Assembly: Derived Classes
  • Same Assembly: Other Classes
  • Other Assemblies: Derived Classes
  • Other Assemblies: Other Classes