We have a system that was written for the .NET framework by a client, and an old developer, who was proficient in the framework, did updates and some work on the system. That developer has now left us.
I'm a backend and frontend developer, with no knowledge in the language or system stated above. My employer wants me to learn the system and languages involved so that the system can be updated and maintained. I have no desire and find no purpose in my learning these languages/systems, but my employer says "Well, I don't know about them either, so you can learn it and teach me".
How/can I refuse to do such work? I know the languages will not interest me in the slightest nor will I use them in the future. Also note, there are two other developers who work with the style of system and the languages on a daily basis.
I'm waiting for tomorrow when my employer is actually in the office before I discuss with him that I refuse to do the work when there are other capable employees to do such work.
So how can I go about this and is this really acceptable? I know that if I don't do it, there is the chance they could sack me.