dataset 判斷整列是否有重複，找出重複資料

DataTable dt = ds.Tables[0];
DataView dv = new DataView(dt);

if (dv.Count != dv.ToTable(true, jsonColumnNameNo).Rows.Count)
{

//有重複 取出重複資料
var repeatData = (from a in dt.AsEnumerable()
group a by a.Field<string>(jsonColumnNameNo)
into g
where g.Count() > 1
select new
{
value = g.Key
}).ToList();

}