i have some code in visual basic and i wrote some classes in c++ and i want make it dll
but i don't know that when you use dlls it decreases the speed of process or not.

Using a DLL does not decrease the speed of a process. Compiled code is compiled code whether it resides in a main module or a library. By putting common code into a DLL, however, you make it available to multiple projects without having to recompile it, and (as far as I know) if several active processes use the same DLL, it only has to be loaded into memory once. Furthermore, when you modify a DLL, you do not have to rebuild and reinstall the programs that use that DLL.

The downside is that you have to be very careful that any changes you make to the DLL do not break any of the programs that use it.

If your program has no references, you can probably bypass the use of the DLL.
It's an integral part of the platform and something that should not cause you worry.

If you are doing cross-language programming in dot net, you absolutely will use a DLL in some manner.

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