How to convert Unix date time in list?

DateTime S_Date;
List<formated> dt=new List<formated>();
Formated f;


List<products> prodlist=ctx.Products.ToList();

foreach(var item in prodlist)
{

S_Date = new DateTime(1970,1,1,0,0,0,0, System.DateTimeKind.Utc); 
S_Date = S_Date.AddSeconds(Convert.ToDouble(item.RecordSubmitTime)).ToLocalTime();

//Storing the data into List<>

f=new Formated();
f.ProdName=item.ProdName;
f.Date=gdate;
dt.Add(f);

}


public class Formated
{
public string ProdName{get;set;}
public DateTime Date{get;set;}
}