C# extension methods

How to Use Extension Methods in C#

Programming requires a person to provide a computer with specific instructions, which is typically a time-consuming operation. We can speak with computers thanks to computer programming languages, but doing so necessitates providing them a long list of directives. For many programmers, extension techniques greatly facilitate this procedure. A programmer can utilize an extension method to avoid having to create an entire method from scratch in order to run the program because it already has the basic structure in place.

There are many different ways to use extension methods in C# programming, and there are some situations when users write their own methods to reuse in subsequent programs. You can use some of the most significant extension methods in the.NET Framework in addition to developing your own if you so choose. Your life as a programmer can be made a lot simpler by combining C# and.NET.

What is an Extension Method?

In the realm of computer programming, extension methods are rather prevalent, and whether a programmer utilizes them in.NET or LINQ, they may accomplish a lot of work with them. In reality, C# is the only program—if not the only one—that naturally permits you to use extension methods with a modicum of simplicity.

Simply said, an extension method allows you to extend a data type in your software. This method defines a static method in a static class in the most basic terms. The first parameter in the method is then identified as the data type that is being extended by the method by identifying the “this” that is put in front of it.

An illustration of an extension method in use may be found below.

.public static class Extensions
  Public static int OneHalf (this int source)
  Return source / 2;

Take note of a few of the program’s main components. The class is named and identified in the first line of the program, public static class Extensions. Take note of the word “static” in the class’s identification. You must ensure the class is static in order to use an extension method.

Public static int OneHalf is the program’s next line (this int source). There are important things in this section of the software that you should also keep in mind. The method begins with this program, which must be static like the class. Additionally, there is the int data type. OneHalf is an integer when used with this enhanced technique.

How Extension Methods Make Programming Easier

public static class ExtensionInt
  public static int OneHalf(this int solution)
    return solution / 2;
    public static int ExponentCube(this int solution)
    return (int)Math.Pow(solution, 3);
    public static int ExponentSquare(this int solution)
    return (int)Math.Pow(source, 2);

The aforementioned techniques show how extension methods can be used to simplify programming. View the aforementioned three approaches. They all solve the same mathematical issue. The first technique divides a number by two. The second technique involves multiplying a number by three exponentially. The second approach does the same task, but takes the integer and multiplies it by two instead of increasing it exponentially by three.

Let’s consider an example where you wished to multiply a value exponentially by 3 or cube it. The new result was then multiplied exponentially by two, and the outcome was eventually divided by two. With conventional programming techniques, you would produce a line of code that was exceedingly difficult. Let’s examine how 25 would traditionally be done in this situation.

var answer = ExtensionsInt.ExponentCube(ExtensionsInt.ExponentSquare(ExtensionsInt.OneHalf(25)));

As you can see from the example above, solving a problem like this requires a lot of nesting. You must make sure that everything is neatly nested together and that it is done in the correct order. If you were to make a mistake, you would need to verify each character in this line of code to ensure that everything still makes sense. Many people make the error of not knowing how many parenthesis are involved in a situation like this.

On the other hand, this line of code would be much shorter if you were to use extension methods.

var answer = 25.ExponentCube().ExponentSquare().OneHalf();

The code above accomplishes the same task as the code you previously saw, but it is much shorter and much simpler to comprehend. If the program makes a mistake, it would be simple to spot as it is so obvious what it is doing. This is the strength of extension methods—they provide you the ability to add functionality to a parameter that you otherwise might not have had. When compared to writing programs without extension methods, your programs will perform considerably more smoothly.

Important things to keep in mind about C# extension methods:

When utilizing C# extension methods, keep the following in mind:

  1. Only the static class may contain definitions of extension methods.
  2. Extension methods should always be specified as static methods, but they will change into non-static methods when they are bound to any class or structure.
  3. The binding argument, which should contain the name of the class to which the method must be bound, should be prefixed with the binding keyword. It is the first parameter of an extension method.
  4. Only one binding parameter can be specified for an extension method, and it must be first in the parameter list.
  5. If necessary, a normal parameter can be added to an extension method definition starting from the second position in the parameter list.
  6. By including the extension method’s namespace, extension methods can be utilized anywhere in the application.
  7. Method overriding is not supported by the extension method.
  8. It has to be defined in a static class at the top level.
  9. Fields, properties, and events are excluded.


  1. The main benefit of the extension method is that it avoids using inheritance to add new methods to the existing class.
  2. Without changing the existing class’s source code, new methods can be added to it.
  3. Additionally, it can be used with closed classes.


Hope this helped you understand what C# extension methods are and how to utilize them. They give us the ability to quickly add additional functionality to an existing type without having to either develop a wrapper for it or inherit from it.

Make careful you don’t misuse it, as you should with other design patterns! Everything has its place. Extension techniques are certainly cool, but they might not

always be the answer to your issue. Therefore, use caution in how and where you choose to utilize them.