c# convert datetime to unix timestamp

public static DateTime UnixTimeStampToDateTime( double unixTimeStamp )
{
    // Unix timestamp is seconds past epoch
    System.DateTime dtDateTime = new DateTime(1970,1,1,0,0,0,0,System.DateTimeKind.Utc);
    dtDateTime = dtDateTime.AddSeconds( unixTimeStamp ).ToLocalTime();
    return dtDateTime;
}

Int32 unixTimestamp = (Int32)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;