ListAllTheThings.cs

public static class Extensions
    {
        public static IEnumerable<DropDownFormat> ToDropDownFormat<T>(this IList<T> list,
            Expression<Func<T, int>> idColumn,
            Expression<Func<T, string>> textColumn)
        {
            List<DropDownFormat> retList = new List<DropDownFormat>();

            var idMemberExp = (MemberExpression)idColumn.Body;
            var textMemberExp = (MemberExpression)textColumn.Body;
            var idName = idMemberExp.Member.Name;
            var textName = textMemberExp.Member.Name;

            foreach (T o in list)
            {
                var typeOfList = typeof(T);
                var id = (int)typeOfList.GetProperty(idName).GetValue(o, null);
                var text = (string)typeOfList.GetProperty(textName).GetValue(o, null);
                var ddf = new DropDownFormat() { Id = id, Text = text };
                retList.Add(ddf);
            }
            return retList.ToList();
        }

    }