Understanding Use Of Properties In C# With Example

A property is a member that provides a way to read, write, and manipulate the value of a private field. Properties can be used as if they are public data members, but internally they are special methods called accessors (get, set). We can say properties are syntactic sugar on getter and setter methods which can be used to set or get private fields. Properties are helpful to achieve the encapsulation feature of object-oriented programming.

Why do we need properties?

I will try to explain this with an example.

Brief information about the below program

I created one Class "Employee" and added three fields _firstName, _lastName, _salary.
Inside the main method I created an object of "Employee" class and assigned values for three fields.

namespace PropertiesDeepDive
{
static class Program
{
private static void Main()
{
Employee emp = new Employee();
emp._firstName = "John";
emp._lastName = null;
emp._salary = -1000;
Console.WriteLine("FirstName:{0}\nLastName: {1} \nSalary: {2}", emp._firstName,emp._lastName, emp._salary);
Console.ReadLine();
}
}
public class Employee
{
public string _firstName;
public string _lastName;
public int _salary;
}
}

Below points clarify what's wrong with the above program:

The very first thing wrong about this program is it is violating Encapsulation principle of OOPS as it is exposing internal details of class to the outside world by making fields public.
The second problem is, in the real world the last name cannot be null or Salary cannot be negative, but in the above program, we can set _lastName to Null and _salary to negative value thus corrupting object of Employee. Also, we cannot restrict the user from assigning the negative value to _salary or Null value to _lastName to solve these issue C# comes up with Properties member.

Syntax For Property

<Access-Modifier> <Type> <PropertyName> {
<Access-Modifier> get {
/*Get Accesser Logic*/
}
<Access-Modifier> set {
/*Set Accesser Logic*/
}
}
/*Example of property*/
public int Salary
{
get
{
return _salary;
}
set
{
_salary = value;
}
}

Property Sytax Explanation

<Access-Modifier>
Can be Public, Protect, Private which decides accessibility.
<Type>
Can be the value type or reference type (eg Class, Interface, struct or any value types like int)
<PropertyName>
It is the name of the property
get
This is called a get accesser and is used to get the value
set
This is known as a set accesser and is used to set the value

Employee class is modified to solve issues that appeared in the first program as below,

Changed _firstName, _lastName, _salary fields from the public to private.
Added three public properties FirstName, LastName and Salary for _firstName, _lastName, _salary fields respectively.
For FirstName and LastName property Inside set accessor, the check for value is Null and if the value is Null it will throw an exception
Also added a check for Salary that if the value is less than or equal to zero itthrows an exception that salary cannot be negative
In the Main class two objects of Employee class emp1 and emp2, for emp1 are assigned correct values for all three fields and in emp2 assigned Null for Lastname and Salary is in the negative

namespace PropertiesDeepDive
{
static class Program
{
private static void Main()
{
Employee emp1 = new Employee();
emp1.FirstName = "John";
emp1.LastName = "Mehar";
emp1.Salary = 1000;
Console.WriteLine("FirstName:{0}\nLastName: {1} \nSalary: {2}",
emp1.FirstName, emp1.LastName, emp1.Salary);
Employee emp2 = new Employee();
emp2.FirstName = "John";
emp2.LastName = null;
emp2.Salary = -1000;
Console.WriteLine("FirstName:{0}\nLastName: {1} \nSalary: {2}",
emp2.FirstName, emp2.LastName, emp2.Salary);
Console.ReadLine();
}
}
public class Employee
{
private string _firstName;
private string _lastName;
private int _salary;
public int Salary
{
get
{
return _salary;
}
set
{
if (value < 0)
throw new Exception("Salary can not be negative");
_salary = value;
}
}
public string FirstName
{
get
{
return _firstName;
}
set
{
if (value == null)
throw new Exception("FirstName can not be Null");
_firstName = value;
}
}
public string LastName
{
get
{
return _lastName;
}
set
{
if (value == null)
throw new Exception("LastName can not be Null");
_lastName = value;
}
}
}
}

Output of the above program,

Program has worked fine for first Employee object i.e emp1 as every field was valid, but in case of emp2 it throws an Exception as LastName is Null as inside LastName property we have written logic to throw an exception if LastName is Null.

What problems does the above program solve?

As _firstName, _lastName, _salary are private it solves the problem of exposing implementation details of class to outside world and hence achieving encapsulation principle.
Also _firstName, _lastName cannot be set to Null as inside set accessor checked if the value is Null and _salary also cannot be set to minus. Thus we are saving our object from getting corrupted due to invalid data.

7 Comments

Join the conversation! Your thoughts help the community grow.

Laxmidhar Sahoo7y ago
Thank you very much
Anil Kumar8y ago
In the Main class two objects of Employee class emp1 and emp2, for emp1 are assigned correct values for all three fields and in emp2 assigned Null for Lastname and Salary is in the negative ........But i can see in emp1 and emp2 the values given are same in main method......by executing the above code how the output with last name Mehar came...there is no Value given for lastname is Mehar....pLease clarify me....
- Anil Kumar8y ago
  Thank you...
- Gajanan Chavhan8y ago
  Good catch. its a Typo. I will update the blog. thank you
- Gajanan Chavhan8y ago
  Updated changes pointed out by you. Thanks.
Viknaraj Manogararajah8y ago
Nice Article...........
Shrimant Telgave8y ago
To understand the encapsulation this blog will help more.