Access
modifiers are an integral part of object-oriented programming. They
support the concept of encapsulation, which promotes the idea of hiding
functionality. Access modifiers allow you to define who does or doesn't
have access to certain features.
In C# there are 5 different types of Access Modifiers.
Modifier
|
Description
|
public
|
There are no restrictions on accessing public members.
|
private
|
Access is limited to within the class definition. This is the default access modifier type if none is formally specified
|
protected
|
Access is limited to within the class definition and any class that inherits from the class
|
internal
|
Access is limited exclusively to classes defined within the current project assembly
|
protected internal
|
Access
is limited to the current assembly and types derived from the
containing class. All members in current project and all members in
derived class can access the variables.
|
public
The public keyword is an access modifier for types and type members. Public access is the most permissive access level. There are no restrictions on accessing public members.
Accessibility:
- Can be accessed by objects of the class
- Can be accessed by derived classes
Example: In the following example num1 is direct access.
using System;
namespace AccessModifiers
{
class Program
{
class AccessMod
{
public int num1;
}
static void Main(string[] args)
{
AccessMod ob1 = new AccessMod();
ob1.num1 = 100;
Console.WriteLine("Number one value in main {0}", ob1.num1);
Console.ReadLine();
}
}
}
private
Private access is the least permissive access level.
Private members are accessible only within the body of the class or the struct in which they are declared.
Accessibility:
- Cannot be accessed by object
- Cannot be accessed by derived classes
Example: In the following example num2 is not accessible outside the class.
using System;
namespace AccessModifiers
{
class Program
{
class AccessMod
{
public int num1;
int num2;
}
static void Main(string[] args)
{
AccessMod ob1 = new AccessMod();
ob1.num1 = 100;
ob1.num2 = 20;
Console.WriteLine("Number one value in main {0}", ob1.num1);
Console.ReadLine();
}
}
}
The
above program will give compilation error, as access to private is not
permissible. In the below figure you can see the private member num2 is
not available.
protected
A
protected member is accessible from within the class in which it is
declared, and from within any class derived from the class that declared
this member. A
protected member of a base class is accessible in a derived class only
if the access takes place through the derived class type.
Accessibility:
- Cannot be accessed by object
- By derived classes
using System;
namespace AccessModifiers
{
class Program
{
class Base
{
protected int num1;
}
class Derived : Base
{
public int num2;
static void Main(string[] args)
{
Base ob1 = new Base();
Derived ob2 = new Derived();
ob2.num1 = 20;
ob2.num2 = 90;
Console.WriteLine("Number2 value {0}", ob2.num2);
Console.WriteLine("Number1 value which is protected {0}", ob2.num1);
Console.ReadLine();
}
}
}
}
In
the above program we try to access protected member in main it is not
available as shown in the picture below that num1 is not listed in
intellisense.
internal
The
internal keyword is an access modifier for types and type members. We
can declare a class as internal or its member as internal. Internal
members are accessible only within files in the same assembly (.dll). In other words, access is limited exclusively to classes defined within the current project assembly.
Accessibility:
In same assembly (public)
- Can be accessed by objects of the class
- Can be accessed by derived classes
In other assembly (internal)
- Cannot be accessed by object
- Cannot be accessed by derived classes
protected internal
The protected internal accessibility means protected OR internal, not protected AND internal.
In other words, a protected internal member is accessible from any class in the same assembly, including derived classes.
The
protected internal access modifier seems to be a confusing but is a
union of protected and internal in terms of providing access but not
restricting. It allows:
- Inherited types, even though they belong to a different assembly, have access to the protected internal members.
- Types that reside in the same assembly, even if they are not derived from the type, also have access to the protected internal members.
Default access
A
default access level is used if no access modifier is specified in a
member declaration. The following list defines the default access
modifier for certain C# types:
enum: The default and only access modifier supported is public.
class: The default access for a class is private. It may be explicitly defined using any of the access modifiers.
interface: The default and only access modifier supported is public.
struct: The default access is private with public and internal supported as well.
The
default access may suffice for a given situation, but you should
specify the access modifier you want to use to ensure proper application
behavior
