Schedule a C# class and method

The easiest an simplest way would be to employ the Windows Task Scheduler[^] service.
 
Build your class into a console application, then use the Task Scheduler to schedule it. This can be done using the GUI (Control Panel → Administrative Tools → Task Scheduler), or at the command line using at[^] or schtasks[^]. The latter is much more flexible.
 
If you would like to do this programatically, you want to develop a Windows NT Service[^]. This is a much bigger task.