Class Vs Structs

Both Classes and Structs are constructs in C# which are used to create custom complex types by encapsulating a set of basic types and logic. Though they are used to create custom types there are some underlying differences between the two, the following are some of the differences between classes and structs.

OUT vs REF Parameters

OUT and REF parameters are almost similar, both are used to return additional values from a function to the code which is calling the function. However there are some difference between the two, the following are the some of the key differences between the OUT and REF parameters.

Out parameters are declared by adding the keyword out in front of the parameter.

REF Parameter

REF parameters are parameters which are passed between the calling function and the function being called, we need to declare and initialize the parameters in the calling method, their values will be re-assigned in the actual function and returned back to the calling function.

REF parameters are declared similar to the normal parameters by adding a ref keyword in front of the parameter as follows.

OUT Parameter

OUT parameters are parameters which are passed back from a function to the calling function or method, it is good enough to declare the parameters in the calling method they need not be initialized in the calling class, instead their values will be assigned in the function which is returning the out parameters.

OUT parameters are declared similar to the normal parameters by adding an out keyword in front of the parameter as follows.

Constants

As the name suggests Constants are a type of class members whose value is defined at the time of writing the program and remain constant forever, the values of constants cannot be changed at runtime, the values of a constant defined in a class will remain same for every instance that is created from the class.

Constants are declared using the const keyword as follows.

Anonymous Types

Anonymous types allow us to define variables and classes dynamically at runtime without having to declare them beforehand. The following example creates a string variable MyName dynamically at runtime without any specific declaration.

    var MyName = "Test Name";

    Console.WriteLine(MyName.GetType());

When this code executes the output will be as follows

Nested Classes

As the name suggests, nested classes are classes which are defined within an outer parent class. The following example creates a nested class called NestedClass which is encapsulated in the outer class called OuterClass.

Destructors

Destructors are used to free unused resources and release memory used by the resources. Destruction of Managed objects are handled by the Garbage collector in the .Net Framework, we can use the destructor to release any unmanaged resources like Network connectivity, database connections etc and release the resources.

The signature of the destructor is similar to a constructor, it shares the same name of the class, the only difference is that we add a ~ symbol in front of the method name to denote that this is a destructor.

The following example defines a destructor for the CEmployee class

Constructors

Constructors are methods of a class which get executed automatically when an instance of a class is created. The constructor method name should be same as the class name.

The following example defines a simple constructor for the class CEmployee

What is an Object?

An object is an instance or representation of a class. Objects are the building blocks of Object Oriented Programming, objects give life to classes and structs. Classes are mere definition of a model,  the model gets activated only when an object is created out of the class.

We can create multiple instances of objects from a single class definition; each object is unique and can hold its own set of values. The fields/properties of an object are used to set/get values to the object while the methods of the object are used to perform some operation on the object.


Let us consider the same Calculator class which we defined in the post What is a Class?, here we shall create an instance of the class, set values to the fields and invoke the methods of the object to see how it operates.

    Calculator objCalculator = new Calculator();

    int nResult = objCalculator.Add(5, 6);

    txtResult.Text = nResult.ToString();

Here objCalculator is the object which represents the class Calculator, the object objCalculator invokes the Add() method of the class and passes values to the method. The object performs the calculation which is defined in its base class definition and returns the result of the calculation, which is captured and displayed in the textbox txtResult in the client application.

What is a Class?

A Class is the basic definition or template of an object, a class defined the properties, methods, events etc of an object. A class is used to represent a real world object/model. For example a calculator can be represented using a Calculator class, the Calculator class defines the properties of a Calculator like input Numbers, operations etc.

A Calculator class just defines the properties and methods of an object, a class does not hold any values of these properties, and to assign values to these we should create an object which represents an instance of the class.

The following example shows a simple Calculator class defined in C#