As in the previous chapters of this book, the programs explained in this chapter will be developed in Visual Studio 2017.

Sample code for this chapter can be found on GitHub at https://github.com/PacktPublishing/Programming-in-C-Exam-70-483-MCSD-Guide/tree/master/Book70483Samples.

All classes, along with their respective attributes and functions, have an access modifier associated with them. An access modifier basically indicates how the respective element will be accessed in the application, both in its own assembly as well as in other assemblies. Collectively, attributes and functions in an application are referred to as class members.

In C#, a class and its class members can acquire the following access modifiers:

• Public: A class or a class member declared as public can be accessed by all classes in the same assembly as well as by classes in different assemblies present in the application.
• Private: A class member declared as private can be accessed only in the same class but not outside it.
• Protected: A class or a class member declared as protected can be accessed inside the class or by classes that inherit from the respective class...

In C#, a variable can acquire one of the following types:

• A value type
• A reference type

C# differentiates between these two types in terms of how these values are saved and maintained in the Global Assembly Cache (GAC) during the program execution. Value type variables are saved in the stack, while reference type variables are saved in a managed heap data structure.

There are other pointer types that allow us to access value in the memory location of a variable. In Chapter 8, Creating and Using of Types in C#, we will explore those data types in detail. For now, let's look at these two data types and explore them in detail.

In value types, the variables contain the data or the...

In the first chapter, we created a basic Hello World program. In this topic, we will extend that program and use it to implement a struct and a class. While doing so, we will analyze the difference between the implementation and use of reference and value type variables. As you are already aware by now, a struct is a value type variable and a class is a reference type variable:

1. Open the Console project created in Chapter 1, Learning the Basic Structure of C#, and declare a CoordinatePoint class with just two member attributes of x and y coordinates. Also create two constructors – one without any parameters and one with two parameters. Please refer to the following code implementation for this:

class CoordinatePoint
{
    public float xCoordinate;
    public float yCoordinate;
    public CoordinatePoint()
    {
    }
    public CoordinatePoint(float x,...

An interface is a collection of properties, methods, and events with just a declaration and no definition. We use them in programming to group together a set of functionalities that must be implemented in classes that, theoretically, are of the same basic type.

Let's look at an example of a car. In a real-world scenario, any implementation of the Car class must implement certain common basic features such as driving, stopping, and accelerating. Along with those, any object that is classified as a car will also have certain features specific to the make of the car, such as Honda or Nissan.

In the preceding example, an interface could help to promote code reuse and maintain structure across all types of Car. What we can do in this case is to declare Car as an interface that all car derivatives, such as Nissan or Honda must implement.

Similar to an...

The topics covered in this chapter are the basics of programming in the C# language. Using access modifiers, we can control access to different properties and methods in different modules of an application. While writing the code, a very common mistake that people make is to declare all the properties and methods as public. This is not the recommended way of programming in C#. We must logically evaluate the need for different access modifiers for each of the properties and methods present in a class.

Similarly, we should analyze the data types that we need to associate with each property used in the class. We must also analyze if we need a reference data type variable, or whether we are fine with a value type variable as they have a different implementation in the compiler memory and functionality. We should also utilize inheritance as it helps us to reuse code and structure...

1. Which of the following attributes declared in the Car class is not a value type variable?
   1. public Decimal fuelCapacity;
   2. public Enum carColor;
   3. public String registrationNumber;
   4. public Int numberOfSeats
2. Which of the following is not a reference type variable?
   1. Class
   2. String
   3. Struct
   4. Interface
3. In C#, a child class can inherit from multiple parent classes. Is this statement correct?
   1. Yes
   2. No
4. Which of the following statements about interfaces and classes is not correct?
   1. A class can implement multiple interfaces.
   2. An interface can have both function declarations and definitions.
   3. A struct data variable cannot inherit from another struct.
   4. In inheritance, if both the base class and the derived class have a function with the same name, we can use the base keyword to implicitly call the function of the base class.
5. Which of the following statements about access modifiers is...

1. public String registrationNumber;. String is a reference type variable. All others are value type variables.
2. Struct is a value type variable unlike all others which are reference type variables.
3. No, in C# we cannot have multiple inheritance. A class can only inherit from one base class.
4. In C#, an interface must only have function declarations and not definitions. All other statements are correct.
5. If a member variable is declared as protected, it can only be accessed in the classes that inherit from its base parent class.