How to write a program that remotely controls windows?

Question

C++ / C#

You need to write something like TeamViewer, but only easier (That is, the exe that will be located on windows will work in the background, and the exe that will be located, for example, I should have a simple window with the desktop of another computer)
PS I do not write any trojan and hope for your help

Answer 1

Then what libraries to use?

e.g. FreeRDP

Answer 2

How to write a program that remotely controls windows?

It's very simple - open the development environment, start writing, and write until you write.
What specifically is not working for you?

Answer 3

Why write: RemoteDesktop

1. Install the Chrome Remote Desktop extension .
   
2. Launch the Chrome browser on your computer.
   
3. Type chrome://apps in the address bar and press Enter.
   
4. Select Chrome Remote Desktop Application Chrome Remote Desktop.
   
5. Under My Computers, click Get Started.
   
6. Click Allow remote connections.
   
7. Enter your PIN, repeat it and press OK.
   
8. Select Yes to set up a host for Chrome Remote Desktop.
   
9. Confirm signing in to your Google account and re-enter your PIN.
   
10. The configured device will appear under My Computers.
    

Answer 4

If you just need to spy on the user without his knowledge - there are a lot of such programs, google it.