try this
List<Prog> lst = new List<Prog> ();
lst.Add( new Prog(){ Program_ = "I", Module = "1,2,3"});
lst.Add( new Prog(){ Program_ = "II", Module = "2,3"});
lst.Add( new Prog(){ Program_ = "III", Module = "1,3"});
int find = 2;
IEnumerable<string> programs = lst.Where(k => k.Module.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries).Select(a => Convert.ToInt32(a)).Contains(find)).Select(x => x.Program_).ToList();
public class Prog
{
public string Program_ { get; set; }
public string Module { get; set; }
}