.NET Guidebook

Functions

.NET Extension Methods

Extension Methods

.NET extension methods add functionality to existing types.

What Are Extension Methods?

In .NET, extension methods allow developers to add new methods to existing types without modifying their source code. They are a special kind of static method but are called as if they were instance methods on the extended type.

Extension methods make it easier to work with types that you do not have control over, such as classes from third-party libraries or the .NET Framework itself.

How to Define an Extension Method

To define an extension method, you must use a static class and a static method. The first parameter of the method specifies which type the method extends and is prefixed with the this keyword.

Here is a simple example that adds a method to the string type:

Using Extension Methods

Once an extension method is defined, it can be called on the instance of the type it extends as if it were a regular method. For example, using the IsPalindrome method on a string:

Benefits of Using Extension Methods

  • Improved Readability: Extension methods can make code more readable by allowing methods to be called as if they were instance methods.
  • Separation of Concerns: They enable functionality to be added without altering the existing codebase.
  • Enhanced Code Organization: Static classes can group related methods, promoting better code organization.

Limitations of Extension Methods

  • Not Overridable: Extension methods cannot override existing methods.
  • Static Context: They must be defined in a static context, which can be limiting for certain types of operations.
  • Discoverability: Since they are not part of the type's original definition, they may not be as easily discoverable by other developers.

Functions

Next
Async Methods