Create an extension method by given a DLL

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Say I get a dll from a third party. It only has one method

DisplayMethod(string result)

Now I want to add a new method PrintMethod(string result)to it but I can't get the dll's source code.
So I guess that I have to generate an extension method to it. But how?

What I have tried:

I know how to create an extension method from the scratch. But not sure how to do it by given dll. Need code example. Thanks

Posted 26-Aug-17 3:19am

Member 12658724

Updated 26-Aug-17 3:41am

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Dave Kreskowiak · Accepted Answer · 2017-08-26T03:41:00

Solution 1

Extension methods apply to types, not .DLL's. Extensions add functionality applicable to a type, like an integer or string.

There is no point to adding an "extension" to a .DLL. Your code cannot make it into the .DLL file itself, so you're just making a new .DLL that would be along side of the existing one in the file system. You're just making a new class library project which will compile into another .DLL.

Now, what would this new method do? Are you trying to replace the DisplayMethod functionality? Is the original method overridable?

Posted 26-Aug-17 3:41am

Dave Kreskowiak

Comments

Member 12658724 26-Aug-17 9:57am

Yes. I was interviewed onsite a few weeks ago. One guy asked me the question, I was/am confused. Then I asked him in reply: why do you create a new dll to do it?

Dave Kreskowiak 26-Aug-17 10:17am

You can't add your code to the original .DLL because, 1) it's a LOT of manual work just to poke it in there and 2) strong named assemblies can't be modified without breaking the security around them.

This is as far as I go because I'm not doing your interview homework for you.