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Need to modify C# compiled dll

Posted on 2010-11-12
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Last Modified: 2012-05-10
Hi!

I have compiled C# dll. And I need to modify one method inside this dll.
The methods looks like:
void func()
{
    MessageBox.Show("Text of message box", "Title", MessageBoxButton.OK, MessageBoxImage.Exclamation);
}
I need to add "return" statement, before MessageBox.
I have installed Olly Debugger, moreover I did search in "Memory dump" window for "Text of message box" and I have found some places(addresses), where this text occurs, but I don't know how to modify(insert return statement) dll in these places using Olly Debugger(is this possible?).
By the way, I know exact method's name, text and so on.(Actually, I do have source code, but I can not recompile this dll using source code. Please, don't ask why.)

Any articles, suggestions, software recommendations, which will help me to achieve my goal, would be highly appreciated!
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Question by:SpringMVC
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Accepted Solution

by:
Richard Lee earned 500 total points
ID: 34119730
What you would be looking for is .NET Reflector (you may need the pro version)
http://www.red-gate.com/products/reflector/

Also you can look into ILASM & ILDASM that come with visual studio
http://blogs.msdn.com/b/thottams/archive/2007/02/01/using-ilasm-and-ildasm.aspx

DaTribe
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Expert Comment

by:Bardobrave
ID: 34119987
Maybe I'm suggesting some too simple, but you can make your change on your source code, recompile and substitute old DLL with new one.

I supose that you've considered this option already and that's not viable on your situation, but hey... you never know...
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Expert Comment

by:Bardobrave
ID: 34119998
Oh sorry, I've just read the end of your post, forget my previous response.

Good luck with DaTribe recommendation.
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Author Comment

by:SpringMVC
ID: 34120146
Tnx for replies.

DaTribe.
Maybe, I am wrong, but .NET Reflector - is just decompiler, since I have already source code, I don't need to use .NET Reflector, or I am wrong?
ILASM & ILDASM - Tnx, I'll look.

Bardobrave.
Ok :)
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LVL 18

Expert Comment

by:Richard Lee
ID: 34120191
Okay my bad. I actually thought they had included the recompilation feature for .NET reflector. I seem to be getting old!

DaTribe
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Expert Comment

by:Richard Lee
ID: 34120198
BTW is you have the source why not just change and recompile in VS?

DaTribe
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Author Comment

by:SpringMVC
ID: 34120238
In short, I have source code, but don't have some project satellites(resources, files aso), which are needed to recompile.
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LVL 19

Expert Comment

by:Bardobrave
ID: 34120384
It seems a though one... if you lack on code dependencies, even if you manage to decompile the DLL you won't be able to compile it back again, because this dependencies won't be present on compilng time.

You'll need some program that allow you to directly edit the content of the compiled DLL, wich I'm not sure if it's possible at all.

As compiling is a conversion from high-level language to low-level machine code I supose that would be possible to "translate" the DLL's source code back and make changes directly on this source.

However, without an application that makes automatically the translation it could be a work as hard as hell.

I'll search for such an app when arriving home, I'll post it here if found something, but I fear that if DaTribe hasn't an ace under it's sleeve you're facing hard time...
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Author Closing Comment

by:SpringMVC
ID: 34120736
ILDASM/ILASM
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Author Comment

by:SpringMVC
ID: 34120772
Tnx for all. I managed to change DLL using ILDASM/ILASM :)

Bardobrave
I translated .dll to .il (intermediate language) using ILDASM, changed .il file using notepad and translated back to dll from changed .il file using ILASM :)
However, tnx for your concern.
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Expert Comment

by:Richard Lee
ID: 34120814
Glad to help. Those tools are the great if you like IL :)
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LVL 19

Expert Comment

by:Bardobrave
ID: 34121925
Good to know it!

This is the best of this site, you always can learn something new and useful while trying to help someone.
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