how to show calculate remain days datable base on Reg Date

Assuming your database is SQL Server (even that you didn't mention!)

select regDate

  ,dateadd(year, 1, regDate) validUpto

  ,datediff(day, getdate(), dateadd(year, 1, regDate)) remainingDays

from table_name

where....

my datatable contain regDate column but i want to calculate result show on new column one which are not in database. validity period is 1yr .

i calculate result and store in array . but problem is how to show to calculated result in new column against perticular record id.

This is a classic example of how someone asking question just assumes that everybody know everything about his/her problem.

What is the validity period? 30 days, 1 year? please mention.

Also, what exactly you want? Do you want just the select query?

Have you tried something already? If yes, please share. If not, please do.

Loads and loads of online mvc tutorials available over Internet. Just google.