What is use of extention method

Vilas Sagar

7y959Learn iOS Programming

The real time example of use of 3xtention method.

7 Replies

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Mageshwaran R6y ago
An extension method is one that is used to extend the functionality of existing types by adding methods sans the need of creating new derived types. You don't need to create subclasses of existing classes or recompile or modify your existing classes to work with extension methods
0
Bidyasagar Mishra7y ago
An extension method is a static method of a static class that can be invoked using the instance method syntax. Extension methods are used to add new behaviors to an existing type without altering. In extension method "this" keyword is used with the first parameter and the type of the first parameter will be the type that is extended by extension method.

Conceptually, extension methods provides as an implementation of the decorator structural pattern. At compile time an extension method call is translated into an ordinary static method call.

A simple Extension Method Example
//defining extension method

public static class MyExtensions

{

public static int WordCount(this String str)

{

return str.Split(new char[] { ' ', '.', ',' }).Length;

}

}



class Program

{

public static void Main()

{

string s = "Dot Net Tricks Extension Method Example";



//calling extension method

int i = s.WordCount();



Console.WriteLine(i);

}

}
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Rajanikant Hawaldar7y ago
Hi Dear,

In Simple terms, Lets say your need some functionality from existing class that class may be from your project or some other class library but problem you don't have persimmion to change class in such case and in some case class is from third-party API so here you have only dll so you can not do anything so to come out of this kind of issue Extension Methods are introduced in C#.

Ask me if have any doubts

Thanks
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Minal Shah7y ago
Hi,

All the bove answers are already explaining about extension method. so here is just small example.

If you have case where you always have to remove HTML tags from string. Then what we can do is create extension method for the same and use wherever required.
public static string RemoveHTMLTag(this string value)
        {
            return Regex.Replace(value, @"<(.|\n)*?>", string.Empty);
        }
Here point to remeber is, method should be static and should be in static class.
Now call this method as :
string email="[email protected]";
email = email.RemoveHTMLTag();
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Sai Kumar Koona7y ago
Hope with previous anwsers you might understand what is Extention method is, now for realtime example is, you might come accross many LINQ extention methods which you might use regularly at your development activities.

https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/how-to-add-custom-methods-for-linq-queries
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Amit Mohanty7y ago
Extension methods allow existing classes to be extended without relying on inheritance or having to change the class's source code. This means that if you want to add some methods into the existing String class you can do it quite easily. Here's a couple of rules to consider when deciding on whether or not to use extension methods:

1. Extension methods cannot be used to override existing methods
2. An extension method with the same name and signature as an instance method will not be called
3. The concept of extension methods cannot be applied to fields, properties or events

For more info check the below link.

https://www.c-sharpcorner.com/UploadFile/puranindia/extension-methods-in-C-Sharp-3-0/

https://www.c-sharpcorner.com/blogs/when-should-we-use-extension-methods-in-c-sharp
0
Jaimin Shethiya7y ago
If create an any extention method then you don't have to create any object of the class. we can used directly that method that we have created in our application.
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