comparing date in c# using visual studio

Question

Hello Friends, i have a database for a project with the column start date, end date, duration.

e.g. if the start date is 01/03/2016; end date 01/03/2017; duration 2years. How do i write the code to check if the project have exceeded the supposed 2years duration and flag it red in my form or gridview table taken from sql database.