FireEye has an excellent breakdown of a Remote Access Trojan in C# - which is quite a feat given the constraints of the .NET Framework.
https://www.fireeye.fr/blog/threat-research/2020/05/analyzing-dark-crystal-rat-backdoor.html
I have written some C# malware as well, it is not easy, but we are all standing on the shoulders of giants.
https://github.com/lockfale/DotNetAVBypass-Master
The inestimable awesome Didler Stevens wrote some incredibly well thought out code the deobfuscated Excel macros
https://isc.sans.edu/diary/26110
Here's some really interesting analysis of malweare written for supercomputers. This is really interesting because these hyperdrive computers do a lot of really useful work with governance data, voting, medicine, and a boatload of other stuff.
https://www.cadosecurity.com/2020/05/16/1318/
Hope everyone is staying safe in these weird times.
S