Doing magic with C# Method Extension

Say, we have a class defined in one of the assemblies shipped with a third party solution. It would be a great help if you could add a helper method to one of the objects. Unfortunately, we do not have the source code. 🙁 What do we do?

In such scenarios, .NET hasn’t left us alone in the desert 😀 The method extension technique will allow us to add our own methods to classes of our choice. Want to see an example? Take the List generics, every list of a generic type has some handy methods. Now we want to add one of ours. Printing each of the element in a list requires us to setup a foreach() loop every time. Why don’t we add an extension method named “Print()” which would print all the elements in a list – one by one? Let’s get our hands dirty!

Facts to remember:
— To extend a class and add method, we must declare a public static class with some name. The name doesn’t matter at all.
— We should define a method with our desired name in that class.
— The first parameter to the method will be “this < Object_we_want_to_extend > parameterName”. Do not forget the “this” keyword. It is the magic wand that does the magic.
— We can pass additional parameters.
— When calling the extended method from the original object, the first parameter is not required to pass. You can ignore it as if it were never there.
— For safety and security the extended method can not access private areas (fields, properties or methods).

So what do all these mean? Show me some codes! Okay, here you go:

The output shall be:

Cool, no? 😀 The code is commented as much as I thought necessary. Feel free to ask a question or submit any feedback you might come up with 🙂

Have fun implementing some extended methods on your own 🙂


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