var result = from c in 你的TABLE
             group c by c.fUId into g
             where g.Count() > 0
             select new { fUId = g.Key, Count = g.Count() };

StringBuilder sel = new StringBuilder();
sel.Append("select fUid ");
sel.Append(",COUNT(*) cc ");
sel.Append("from tOrder ");
sel.Append("group by fUid ");
//一般的連線取資料的方式，就不說明了
DataTable dt = GetDt(sel);
List<tClass> tc = (from x in dt.AsEnumerable()
                   select new tClass
                   {
                       fUid = x.Field<string>("fUid"),
                       cc = x.Field<string>("cc")
                   }).ToList();

public class tClass
{
    public string fUid { get; set; }
    public string cc { get; set; }
}

不管是需要排序還是要做什麼，LIST基本都有支援

改成用lambda的寫法就會是這樣

Table.GroupBy(x => new {x.fUId })
                .Select(x => new {fUId  = x.Key.fUId , count = x.Count()}).Where(y=>y.count>0);