Skip to main content

Lambda Expressions in C# Explained


Lambda Expressions in C#

Lambda expressions are anonymous functions that contain expressions or sequence of operators.
All lambda expressions use the lambda operator =>, that can be read as “goes to” or “becomes”. The left side of the lambda operator specifies the input parameters and the right side holds an expression or a code block that works with the entry parameters. Usually lambda expressions are used as predicates or in place of a delegates (a type that references a method).

A lambda expression is an expression of any of the following two forms:
1.     Expression lambda that has an expression as its body:
Example
(input-parameters) => expression
2.     Statement lambda that has a statement block as its body:
Example
(input-parameters) => { <sequence-of-statements> }

Lambda Operator

Use the lambda declaration operator => to separate the lambda's parameter list from its body.
To create a lambda expression, you specify input parameters (if any) on the left side of the lambda operator and an expression or a statement block on the other side. In other words, the lambda operator => divides a lambda expression into two parts. The left side is the input parameter and the right side is the lambda body.

Example

using System;
using System.Collections.Generic;

namespace LegalManagementSystem.Models
{
    public class CsharpnaijaLambda
    {
        public static void Main()
        {
            // sample list of integers
            List<int> list = new List<int>() { 1, 2, 3, 4, 5, 6 };
            //get all even numbers from the sample list above
            List<int> evenNumbers = list.FindAll(x => (x % 2) == 0);
            Console.WriteLine("==============================================");
            foreach (var num in evenNumbers)
            {
                Console.Write("{0} ", num);
            }
            Console.WriteLine("==============================================");
            Console.ReadLine();
        }
    }
}

The preceding example loops through the entire collection of numbers and each element (named x) is checked to determine if the number is a multiple of 2 (using the Boolean expression (x % 2) == 0).

Lambda Example with objects

using System;
using System.Collections.Generic;
using System.Linq;

namespace LegalManagementSystem.Models
{
    public class CsharpnaijaLambda
    {
        public static void Main()
        {
            List<Cat> dogs = new List<Cat>() {
            new Cat { Name = "Musty", Age = 4 },
            new Cat { Name = "Hasdoo", Age = 0 },
            new Cat { Name = "fancy", Age = 3 }
            };

            var names = dogs.Select(x => x.Name);
            foreach (var name in names)
            {
                Console.WriteLine(name);

            }
            Console.ReadLine();
        }
    }
}
class Cat
{
    public string Name { get; set; }
    public int Age { get; set; }
}
We create a collection, containing data from a certain class. In the example, from the class Cat (with properties Name and Age), we want to get a list that contains all the cat's names. With the keyword var, we tell the compiler to define the type of the variable depending on the result that we assigned on the right side of the equals sign.

Example of Lambda Expressions with Anonymous Types

using System;
using System.Collections.Generic;
using System.Linq;

namespace LegalManagementSystem.Models
{
    public class CsharpnaijaLambda
    {
        public static void Main()
        {
            List<Cat> cats = new List<Cat>() {
         new Cat { Name = "Fancy", Age = 4 },
         new Cat { Name = "musty", Age = 0 },
         new Cat { Name = "saki", Age = 3 }
      };
            var newCatsList = cats.Select(x => new {Age= x.Age, FirstLetter = x.Name[0] });
            foreach (var item in newCatsList)
            {
                Console.WriteLine(item);
            }
            Console.Read();
        }
    }
}
class Cat
{
    public string Name { get; set; }
    public int Age { get; set; }
}
The newly created collection newCatsList has elements of an anonymous type taking the properties Age and FirstLetter as parameters.

Sorting using a lambda expression 

The following is an example of sorting with a lambda expression:
public class CsharpnaijaLambda
    {
        public static void Main()
        {
            List<Cat> cats = new List<Cat>() {
         new Cat { Name = "Rex", Age = 4 },
         new Cat { Name = "Sean", Age = 0 },
         new Cat { Name = "Stacy", Age = 3 }
      };
            var newCatsList = cats.Select(x => new { x.Age, FirstLetter = x.Name[0] });
            var sortedCats = cats.OrderByDescending(x => x.Age);
            foreach (var cat in sortedCats)
            {
                Console.WriteLine(string.Format("Dog {0} is {1} years old.", cat.Name, cat.Age));
            }
            Console.Read();
        }
    }

References

1.      c-sharpcorner article   accessed on 23/03/2020
2.      Microsoft Documentation accessed on 23/03/2020
3.      Tutorials Teacher accessed on 23/03/2020


Labels:
Location: Abuja, Nigeria

Comments

Post a Comment

Popular posts from this blog

Classes in C# Explained

C# Class Explained A class is nothing but an encapsulation of properties and methods that are used to represent a real-time entity, as explained by Guru99 . For instance, if you want to work with Guest’s data as in our previous DataDriven Web application . The properties of the Guest would be the Id, GuestName, Address, Phone number etc of the Guest. The methods would include the entry and modification of Guest data. All of these operations can be represented as a class in C# as shown below. using System; namespace CsharpnaijaClassTutorial {     public class Guest     {         public int Id { get ; set ; }         public string GuestName { get ; set ; }         public string Address { get ; set ; }         public string WhomToSee { get ; set ; }     ...
1 comment
Read more

ASP.NET MVC Views

Views in ASP.NET MVC Application explained Find a related article By  Steve Smith  and  Luke Latham from Microsoft Corporation here In the Model-View-Controller (MVC) pattern, the  view  handles the application's data presentation and user interaction. A view is an HTML template with embedded  Razor markup . Razor markup is code that interacts with HTML markup to produce a webpage that's sent to the client. In ASP.NET MVC, views are  .cshtml  files that use the  C# programming language  in Razor markup. Usually, view files are grouped into folders named for each of the application's  controllers . The folders are stored in a  Views  folder at the root of the application as shown: The  Home  controller is represented by a  Home  folder inside the  Views  folder.  The  Home  folder contains the views for the  About ,  Contact , and  Index...
Post a Comment
Read more

ASP.NET MVC Routing

ASP.NET MVC Routing ASP.NET MVC routing is a pattern matching system that is responsible for mapping incoming browser requests to specified MVC controller actions. When the ASP.NET MVC application launches then the application registers one or more patterns with the framework's route table to tell the routing engine what to do with any requests that matches those patterns. When the routing engine receives a request at runtime, it matches that request's URL against the URL patterns registered with it and gives the response according to a pattern match. Routing pattern is as follows A URL is requested from a browser, the URL is parsed (that is, break into controller and action), the parsed URL is compared to registered route pattern in the framework’s route table, if a route is found, its process and send response to the browser with the required response, otherwise, the HTTP 404 error is send to the browser. Route Properties ASP.NET MVC routes are res...
Post a Comment
Read more