Hi there.

I have been programming in VB .Net for a while and I often see questions regarding "dll"s. What are they? Why are they used?

Also, I've noticed that a lot of people are asking about dll injection. What is it, and why is it always looked upon critically?

Thanks for the help.

DLL are like lib files but lib files are integrated into your EXE at compile time; DLL are lib files that the EXE looks for at run time. The reason for using "module" style library files is because they can be used by many different EXE applications and system processes. DLL are binary just like EXE files on windows and can be opened by Assembly debuggers when unprotected.

When you inject a DLL, like say, into an OpenGL or DirectX game. You add a chunk of your own code into the EXE to get access to the insides of the game. One example of why you would want to do this is to toggle the renderer's wireframe mode on or off to be able to see through walls in the game and see other players waiting around corners.

For your case in VB there are DLL's you might need to package along with your EXE so that people you give your software to can run the application without having to look for all of the individual files needed. As a developer, your computer has files that normal users don't already have. Packaging the correct library files is important if you want your clients to open your creations.

DLL = Dynamic-link library
simple to Kanvus answer it contain a custom fuction (that you or other make ) and you can add them any time you want (in your classes modules etc.) they remain used only in the object you use them

you can look at DLLs like a class or module that you can add only if you need it. but if you use it in your code the PC you want to run your program will need to have that dll too

This post has been edited by NoBrain: 4 Sep, 2009 - 01:50 PM

I also wanted to point out the fact that utilizing DLL's allows for better maintenance of the project, as well as aid in the ability to future-proof the project. If your software hits the shelves, and a problem is found, it is much easier to 'patch' the system by upgrading one DLL, instead of requiring a re-compile of the whole project, which would require the end user to re-install the software.

You will also realize (especially when working in an environment with multiple developers) that DLL's allow for a more dynamic code reuse environment. Programmer A writes a DLL to handle TCP Server tasks. Programmer B starts a new project that just so happens to need to utilize similar functionality as your project. Programmer B can reference Programmer A's DLL in his project, and has saved him/herself a lot of time by not having to reinvent the wheel.