C# 4 and .NET 4

Modifiers ❘ 99
modifiers
You have already encountered quite a number of so-called modifiers — keywords that can be applied to a
type or to a member. Modifiers can indicate the visibility of a method, such as public or private, or the
nature of an item, such as whether a method is virtual or abstract. C# has a number of modifiers, and at
this point it’s worth taking a minute to provide the complete list.
Visibility modifiers
Visibility modifiers indicate which other code items can view an item.
modifier OPPlies To desCriPTion
public Any types or members The item is visible to any other code.
protected
internal
Any member of a type, also any
nested type
Any member of a type, also any
nested type
The item is visible only to any derived type.
The item is visible only within its containing
assembly.
private Any types or members The item is visible only inside the type to
which it belongs.
protected internal
Any member of a type, also any
nested type
The item is visible to any code within its containing
assembly and also to any code inside
a derived type.
Note that type definitions can be internal or public, depending on whether you want the type to be visible
outside its containing assembly.
public class MyClass
{
// etc.
You cannot define types as protected, private, or protected internal because these visibility levels would be
meaningless for a type contained in a namespace. Hence, these visibilities can be applied only to members.
However, you can define nested types (that is, types contained within other types) with these visibilities
because in this case the type also has the status of a member. Hence, the following code is correct:
public class OuterClass
{
protected class InnerClass
{
// etc.
}
// etc.
}
If you have a nested type, the inner type is always able to see all members of the outer type. Therefore, with
the preceding code, any code inside InnerClass always has access to all members of OuterClass, even
where those members are private.
other modifiers
The modifiers in the following table can be applied to members of types and have various uses. A few of
these modifiers also make sense when applied to types.
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