A Simple way to Implement Lazy Loading

What is Lazy Loading?

Lazy Loading is an important paradigm to defer initialization of an object until the point at which it is needed.

Why we need it?

For making Application to:

Run faster
Consume less memory

In this article, I’ll show how to implement Lazy Loading.

Let us create a class Company which contains two properties, CompanyName and Employees. We will initialize CompanyName in Company constructor and initialize Employees only when we need it.

public class Company
{
public string CompanyName;
public Lazy < List < Employee >> Employees = null; //1. Mark Employees property as Lazy
public Company()
{
CompanyName = "MNC";
Employees = new Lazy < List < Employee >> (() => getEmployees()); // 2. Asking the property to load values from getEmployees() method
}
//Method to get Employees.
public List < Employee > getEmployees()
{
List < Employee > Employees = new List < Employee >
{
new Employee
{
FirstName = "Sridhar", LastName = "Adusumilli"
}, new Employee
{
FirstName = "Manas", LastName = "Mohapatra"
}
};
return Employees;
}
}
//Employee Class which contains FirstName and LastName properties
public class Employee
{
public string FirstName
{
get;
set;
}
public string LastName
{
get;
set;
}
}

Now, we will initialize Employees property by using cmp.Employees.Value.

class Program
{
static void Main(string[] args)
{
Company cmp = new Company();
Console.WriteLine(cmp.CompanyName);
foreach(var item in cmp.Employees.Value) //3. When we call cmp.Employees.Value then only the Employee list will be populated.
{
Console.WriteLine(item.FirstName + " " + item.LastName);
}
Console.ReadLine();
}
}

Complete Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace SampleLazyLoading
{
class Program
{
static void Main(string[] args)
{
Company cmp = new Company();
Console.WriteLine(cmp.CompanyName);
foreach(var item in cmp.Employees.Value) //3. When we call cmp.Employees.Value then the Employee list will be populated here.
{
Console.WriteLine(item.FirstName + " " + item.LastName);
}
Console.ReadLine();
}
}
public class Company
{
public string CompanyName;
public Lazy < List < Employee >> Employees = null; //1. Mark Employees property as Lazy
public Company()
{
CompanyName = "MNC";
Employees = new Lazy < List < Employee >> (() => getEmployees()); // 2. Asking the property to load values from getEmployees() method
}
//Method to get Employees.
public List < Employee > getEmployees()
{
List < Employee > Employees = new List < Employee >
{
new Employee
{
FirstName = "Sridhar", LastName = "Adusumilli"
}, new Employee
{
FirstName = "Manas", LastName = "Mohapatra"
}
};
return Employees;
}
}
//Employee Class which contains FirstName and LastName properties
public class Employee
{
public string FirstName
{
get;
set;
}
public string LastName
{
get;
set;
}
}
}

Conclusion

We need to check carefully whether the values pertaining to property initialization has been called otherwise the application will be at a risk of null exception.