I'm pondering some ideas for building a DLL for some common stuff I do. One thing I'd like to check if it's possible is running a thread inside of a DLL. I'm sure I would be able to at least start it, and have it automatically free on terminate (and make it forcefully terminate its self) - that I can see wouldn't be much of a problem. But once I start it, I don't see how I can continue communicating with it (especially to stop it) mainly because each call to the DLL is unique (as far as my knowledge tells me) but I also know very little of the subject.

I've seen how in some occasions, a DLL can be loaded at the beginning and released at the end when it's not needed anymore. I have 0 knowledge or experience with this method, other than just seeing something related to it, couldn't even tell you what or how, I don't remember. But is this even possible?

I know about ActiveX/COM but that is not what I want - I'd like just a basic DLL that can be used across languages (specifically C#).

Also, if it is possible, then how would I go about doing callbacks from the DLL to the app? For example, when I start the thread, I most probably will assign a function (which is inside the EXE) to be the handler for the events (which are triggered from the DLL).

So I guess what I'm asking is - how to load a DLL for continuous work and release it when I'm done - as opposed to the simple method of calling individual functions in the DLL as needed. In the same case - I might assign variables or create objects inside the DLL. How can I assure that once I assign that variable (or create the object), how can I make sure that variable or object will still be available the next time I call the DLL? Obviously it would require a mechanism to Initialize/Finalize the DLL (I.E. create the objects inside the DLL when the DLL is loaded, and free the objects when the DLL is unloaded).

EDIT: In the end, I will wrap the DLL inside of a component, so when an instance of the component is created, DLL will be loaded and a corresponding thread will be created inside the DLL, then when the component is free'd, the DLL is unloaded. Also need to make sure that if there are for example 2 of these components, that there will be 2 instances of the DLL loaded for each component.

Is this in any way related to the use of an IInterface? Because I also have 0 experience with this.

No need to answer it directly with sample source code - a link to a good tutorial would be great.