How do i change my c# code to be compatible with sql server

Question

I have a windows forms application that i developed using csharp and access database,i now want to upgrade to sql server because of its advantages over access database. I have so far converted the database to sql server and everything looks good. I understand i need to make some modifications to my csharp code to be compatible with sql server logic and am wondering what the best and fast approach i should take. Any advice is welcome