In C what is the difference between public private protected and having no access modifier

Question

All my college years I have been using public  and would like to know the difference between public  private  and protected   Also what does static do as opposed to having nothing

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mmm     Static means that you can access that function without having an instance of the class    You can access directly from the class definition

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A graphical overview  summary in a nutshell   Since static classes are sealed  they cannot be inherited  except from Object   so the keyword protected is invalid on static classes   For the defaults if you put no access modifier in front  see here  Default visibility for C  classes and members  fields  methods  etc    Non-nested enum                              public non-nested classes   structs      internal interfaces                        internal delegates in namespace            internal class struct member s             private delegates nested in class struct  private  Nested  nested enum      public nested interface public nested class     private nested struct    private  Also  there is the sealed-keyword  which makes a class not-inheritable  Also  in VB NET  the keywords are sometimes different  so here a cheat-sheet

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C  has  in total  6 access modifiers   private  The member declared with this accessibility can be visible within the containing type  it is not visible to any derived types  other types in the same assembly or types outside of the containing assembly  i e   access is limited to the containing type only    protected  The member declared with this accessibility can be visible within the types derived from the containing type within the containing assembly  and the types derived from the containing type outside of the containing assembly  i e   access is limited to derived types of the containing type    internal  The member declared with this accessibility can be visible within the assembly containing this member  it is not visible to any assembly outside of the containing assembly  i e   access is limited to containing assembly only    internal protected  The member declared with this accessibility can be visible within the types derived from the containing type within or outside of the containing assembly  it is also visible to any types within the containing assembly  i e   access is limited to containing assembly or derived types    public  The member declared with this accessibility can be visible within the assembly containing this member  or any other assembly that references the containing assembly  i e   access is not limited   In C  7 2  a new level of accessibility was added   private protected  The member declared with this accessibility can be visible within the types derived from this containing type within the containing assembly  It is not visible to any types not derived from the containing type  or outside of the containing assembly  i e   the access is limited to derived types within the containing assembly   Source including a sample code of the new private protected access modifier

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All access modifiers  descriptions for C

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Hmm   See here   Access Modifiers   In a nutshell   Public gives the method or type complete visibility from other types classes   Private allows only the type containing the private method variable access to the private method variable  note that nested classes  also have access to the containing classes private methods variables    Protected is similar to private except derived classes can also access protected methods    Nothing  is VB NET s equivalent to null  Although if you re referring to  nothing  meaning  no access modifier   then it depends  although a very rough rule of thumb  certainly in C   is that if you don t explicitly specify an access modifier  the method variable declaration is usually as restricted as it can be  i e    public class MyClass       string s           is effectively the same as   public class MyClass       private string s           The linked MSDN article will offer a fully description when there s no access modifier explicitly specified

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using System   namespace ClassLibrary1       public class SameAssemblyBaseClass               public string publicVariable    public           protected string protectedVariable    protected           protected internal string protected InternalVariable    protected internal           internal string internalVariable    internal           private string privateVariable    private           public void test                            OK             Console WriteLine privateVariable                   OK             Console WriteLine publicVariable                   OK             Console WriteLine protectedVariable                   OK             Console WriteLine internalVariable                   OK             Console WriteLine protected InternalVariable                        public class SameAssemblyDerivedClass   SameAssemblyBaseClass               public void test                         SameAssemblyDerivedClass p   new SameAssemblyDerivedClass                    NOT OK                Console WriteLine privateVariable                   OK             Console WriteLine p publicVariable                   OK             Console WriteLine p protectedVariable                   OK             Console WriteLine p internalVariable                   OK             Console WriteLine p protected InternalVariable                        public class SameAssemblyDifferentClass               public SameAssemblyDifferentClass                         SameAssemblyBaseClass p   new SameAssemblyBaseClass                    OK             Console WriteLine p publicVariable                   OK             Console WriteLine p internalVariable                   NOT OK                Console WriteLine privateVariable                   Error    ClassLibrary1 SameAssemblyBaseClass protectedVariable  is inaccessible due to its protection level               Console WriteLine p protectedVariable                   OK             Console WriteLine p protected InternalVariable                          using System          using ClassLibrary1          namespace ConsoleApplication4        class DifferentAssemblyClass               public DifferentAssemblyClass                         SameAssemblyBaseClass p   new SameAssemblyBaseClass                    NOT OK                Console WriteLine p privateVariable                   NOT OK                Console WriteLine p internalVariable                   OK             Console WriteLine p publicVariable                   Error    ClassLibrary1 SameAssemblyBaseClass protectedVariable  is inaccessible due to its protection level                Console WriteLine p protectedVariable                   Error    ClassLibrary1 SameAssemblyBaseClass protected InternalVariable  is inaccessible due to its protection level                Console WriteLine p protected InternalVariable                        class DifferentAssemblyDerivedClass   SameAssemblyBaseClass               static void Main string   args                        DifferentAssemblyDerivedClass p   new DifferentAssemblyDerivedClass                    NOT OK                Console WriteLine p privateVariable                   NOT OK               Console WriteLine p internalVariable                   OK             Console WriteLine p publicVariable                   OK             Console WriteLine p protectedVariable                   OK             Console WriteLine p protected InternalVariable                SameAssemblyDerivedClass dd   new SameAssemblyDerivedClass                dd test

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Those access modifiers specify where your members are visible  You should probably read this up  Take the link given by IainMH as a starting point   Static members are one per class and not one per instance

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Public - If you can see the class  then you can see the method  Private - If you are part of the class  then you can see the method  otherwise not   Protected - Same as Private  plus all descendants can also see the method   Static  class  - Remember the distinction between  Class  and  Object     Forget all that   They are the same with  static     the class is the one-and-only instance of itself   Static  method  - Whenever you use this method  it will have a frame of reference independent of the actual instance of the class it is part of

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Careful  Watch the accessibility of your classes  Public and protected classes and methods are by default accessible for everyone  Also  Microsoft isn t very explicit in showing access modifiers  public  protected  etc   keywords  when new classes in Visual Studio are created  So  take good care and think about the accessibility of your class because it s the door to your implementation internals

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public - can be access by anyone anywhere  private - can only be accessed from with in the class it is a part of  protected - can only be accessed from with in the class or any object that inherits off of the class   Nothing is like null but in VB  Static means you have one instance of that object  method for every instance of that class

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Regarding the question of Nothing   Namespace types are internal by default Any type member  including nested types are private by default

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Reposting the awesome diagrams from this answer      Here are all access modifiers in Venn diagrams  from more limiting to more promiscuous       private          private protected  - added in C  7 2         internal          protected          protected internal          public

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Access modifiers From docs microsoft com   public The type or member can be accessed by any other code in the same assembly or another assembly that references it  private The type or member can only be accessed by code in the same class or struct  protected The type or member can only be accessed by code in the same class or struct  or in a derived class  private protected  added in C  7 2  The type or member can only be accessed by code in the same class or struct  or in a derived class from the same assembly  but not from another assembly  internal The type or member can be accessed by any code in the same assembly  but not from another assembly  protected internal The type or member can be accessed by any code in the same assembly  or by any derived class in another assembly   When no access modifier is set  a default access modifier is used  So there is always some form of access modifier even if it s not set  static modifier The static modifier on a class means that the class cannot be instantiated  and that all of its members are static  A static member has one version regardless of how many instances of its enclosing type are created  A static class is basically the same as a non-static class  but there is one difference  a static class cannot be externally instantiated  In other words  you cannot use the new keyword to create a variable of the class type  Because there is no instance variable  you access the members of a static class by using the class name itself  However  there is a such thing as a static constructor  Any class can have one of these  including static classes  They cannot be called directly  amp  cannot have parameters  other than any type parameters on the class itself   A static constructor is called automatically to initialize the class before the first instance is created or any static members are referenced  Looks like this  static class Foo         static Foo                 Bar    quot fubar quot                  public static string Bar   get  set       Static classes are often used as services  you can use them like so  MyStaticClass ServiceMethod

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A status of Private indicates that variables can only be accessed by objects of the same class  Protected status extends that access to include descendants of the class as well    from the above table we can see the deference between private and protected    am think both are same     so what the need for that two separate command   Check MSDN link for more information

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I think it is related to good OOP design  If you are a developer of a library you want to hide the inner workings of your library  That way  you can modify your library inner workings later on  So you put your members and helper methods as private  and only interface methods are public  Methods that should be overwritten should be protected

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Yet another visual approach of the current access modifier  C  7 2   Hopefully the schema helps to remember it easier  click the image for interactive view    Outside Inside If you struggle to remember the two-worded access modifiers  remember outside-inside   private protected  private outside  the same assembly  protected inside  same assembly  protected internal  protected outside  the same assembly  internal inside  same assembly

[c#] In C#, what is the difference between public, private, protected, and having no access modifier?

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