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Extension methods enable you to "add" methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. Extension methods are static methods, but they're called as if they were instance methods on the extended type.
Extension methods are static because they get the instance passed in via the first parameter, and they don't act on the actual instance of their declaring class. Also, they're just a syntactic sugar. CLR doesn't support such a thing.
The only difference between a regular static method and an extension method is that the first parameter of the extension method specifies the type that it is going to operator on, preceded by the this keyword.
Actually I'm answering the question of why extension methods cannot work with static classes. The answer is because extension methods are compiled into static methods that cannot recieve a reference to a static class.
In short, no, you can't.
Long answer, extension methods are just syntactic sugar. IE:
If you have an extension method on string let's say:
public static string SomeStringExtension(this string s)
{
//whatever..
}
When you then call it:
myString.SomeStringExtension();
The compiler just turns it into:
ExtensionClass.SomeStringExtension(myString);
So as you can see, there's no way to do that for static methods.
And another thing just dawned on me: what would really be the point of being able to add static methods on existing classes? You can just have your own helper class that does the same thing, so what's really the benefit in being able to do:
Bool.Parse(..)
vs.
Helper.ParseBool(..);
Doesn't really bring much to the table...
specifically I want to overload
Boolean.Parseto allow an int argument.
Would an extension for int work?
public static bool ToBoolean(this int source){
// do it
// return it
}
Then you can call it like this:
int x = 1;
bool y = x.ToBoolean();
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