Could you tell me how I can put an associated file in the registry for my player?

I have a player developed in Visual Studio, I put it to open only in single instance to receive all parameters in case it opens several files with it, however this will only work if I take several files and drop them on its .exe files.

I already tried to associate it with CMD and regedit, but I couldn't, always when I select several files in explorer and open, the software receives several socilitations to open only with the first parameter of each file.

I use K-Lite on it to support more formats, and I saw that you know how to create perfect records, and I was wondering if you could help me with that?

Explorer will open a new instance for each selected file. You need to implement code in your player to handle that situation.

The player from K-Lite uses GPL open source license. So you can't use that code as example because then you must open source your player as well.