How do you build a batch process which will run at specific days and times in c# ?

you dont provide a lot of information on what you're trying to achieve apart from 'batch process'

- do need need fault tolerance, recovery after failure, persistence, logging, monitoring, access control etc.
- What is a batch process - a number of executables (exe's) held together by DOS script or some other script ?
- given the previous question, what is the 'granularity' of failure
- do you want emails on 'failed processes'
- is this a fully automated or partially automated workflow ?
- What version of windows etc you have

So you make it a bit hard to answer except in very general terms - for a start, you could consider :-

option 1 : a set of c# console programs/dos scripts scheduled by Quartz.Net running 'standalone' or the Windows task scheduler

option 2 : a Windows 32 Service in c# using embedded Quartz.Net running tasks (exe's) as 'assemblies'

These 2 options are easy enough to start, but you need to add all the framework yourself

option 3 : A fully fledged batch processor costing $$ (there are some nice ones Ive used in the past - ActiveBatch, JAMS Scheduler to name two)

There's umpteen ways to skin a cat - but without detailed requirements etc I cant tell which knife to use

[edit add Visual Cron, Adtempus to the list of 'fully fledged' batch processors - Ive used ActiveBatch and AdTempus extensively, depending on your requirements, they could be a match if you had some cash - not a large amount for AdTempus]