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//////////////////// Don't EVER use public member variables. Why not? ///////////////////////

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                                                                                           //

class Student                                                                              //

{                                                                                          //

    public string name; // Bad...! Bad...!                                                 //

}                                                                                          //

                                                                                           //

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// Imagine that your class is distributed and used in very many places, as the code grows. //

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                                                                                           //

Student student1 = new Student();               // A student is created.                   //

student1.name = "John Doe";                     // Note we are setting a name.             //

                                                                                           //

Student student1000000 = new Student();         // Imagine there are millions of students. //

student1000000.name = "Jane Doe";               // Note we are setting a name.             //

                                                                                           //

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// Note that we directly accessed public variable "name" potentially millions of times.    //

// Now imagine the business requirements change one day, and business makes a new request. //

// They ask you to print the Student's name *every time it changes*.                       //

// They also want to keep track of how many times *any Student's name changed*.            //

// You would have to find potentially millions of lines of code where you set the name.    //

// You would then have to add millions of lines of code to print the Student's name.       //

// You would then have to add millions of lines of code to update the count of changes.    //

/////////////////////////////////////////////////////////////////////////////////////////////

​

// Now, see the alternative.

​

class BetterStudent

{

    private string name;  // Notice this is now PRIVATE.

​

    // Public SET method can set the value in a controlled way.

​

    public void setName(string name)

    {

        // Added code without breaking the invocations.

        string output = "";

        output += "Name changing from " + this.name + " ";

        output += "to " + name + ".\n";

        System.Console.WriteLine(output);

​

        // Originally code which was referenced publicly.

​

        this.name = name;

    }

​

    // Constructor can initialize the name in a controlled way.

​

    public BetterStudent(string name)

    {

        this.name = name;                                                   // Originally code which was referenced publicly.

        System.Console.Write("Name is initialized to " + name + ".\n\n");   // Added code without breaking the invocations.

    }

}

​

// Take note, now, that you never have to make changes to the invocations as long as the method signature doesn't change.

// If the method signature is always [void setName(string)] you can change code in the method body and it will not break.

// All of the invocation points will change the way they work based on the updated class, without changing the invocations.

// Thus in the example above, you would not have to change millions of public access points, just change one method.

​

BetterStudent betterStudent1 = new BetterStudent("John");

BetterStudent betterStudent2 = new BetterStudent("Jane");

betterStudent1.setName("John Doe");

betterStudent2.setName("Jane Doe");