Access modifiers are keywords used to control access to a member (method/member variables/properties) or a type. Following are the access modifiers available in c#

Private

• Only Accessible in the class they are declared.
• Cannot be applied to types (classes, structs etc.) directly under a namespace, but can be used for sub classes (class defined inside a class) or sub structs.

Protected

• Accessible in the class they are declared
• Accessible in all derived classes in any assembly
• Cannot be applied to types (classes, structs etc.) directly under a namespace, but can be used for sub classes (class defined inside a class) or sub structs.

Internal

• Accessible anywhere in the same assembly they are declared in
• Can be applied to types (e.g internal class xyz { ... }) & members

Protected Internal

• Accessible anywhere in the same assembly they are declared in
• Outside the assembly accessible only to classes derived from the class they are declared in
• Cannot be applied to types (classes, structs etc.) directly under a namespace, but can be used for sub classes (class defined inside a class) or sub structs.

Public

• Accessible anywhere without restrictions
• Can be applied to types & members