C# 0 The Complete Reference

C#’s Access Modifiers

Member access control is achieved through the use of four 

access modifiers

:

public

,

private

,

protected

, and 

internal

. In this chapter, we will be concerned with 

public

 and 

private

. The 

protected

 modifier applies only when inheritance is involved and is described in Chapter 11. 

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The

internal

 modifier applies mostly to the use of an 

assembly, 

which for C# loosely means 

a deployable program or library. The 

internal

 modifier is examined in Chapter 16.

When a member of a class is modified by the 

public

 specifier, that member can be 

accessed by any other code in your program. This includes methods defined inside other 

classes.

When a member of a class is specified as 

private

, then that member can be accessed only 

by other members of its class. Thus, methods in other classes are not able to access a 

private

member of another class. As explained in Chapter 6, if no access specifier is used, a class 

member is private to its class by default. Thus, the 

private

 specifier is optional when creating 

private class members.

An access specifier precedes the rest of a member’s type specification. That is, it must 

begin a member’s declaration statement. Here are some examples:

public string errMsg;

private double bal;

private bool isError(byte status) { // ...

To understand the difference between 

public

 and 

private

, consider the following 

program:

// Public vs. private access.

using System;

class MyClass {

  private int alpha; // private access explicitly specified

  int beta;          // private access by default

  public int gamma;  // public access

  // Methods to access alpha and beta. It is OK for a member

  // of a class to access a private member of the same class.

  public void SetAlpha(int a) {

    alpha = a;

  }

  public int GetAlpha() {

    return alpha;

  }

  public void SetBeta(int a) {

    beta = a;

  }

  public int GetBeta() {

    return beta;

  }

}

class AccessDemo {

  static void Main() {

    MyClass ob = new MyClass();

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