/* eklenmesi gerekenler
using System;
using System.Data;
using System.Linq;
*/
public Tuple<int, int> GetCount(DataTable dt, int min, int max)
{
var result = dt.AsEnumerable().Where(num => num.Field<int>("number") >= min && num.Field<int>("number") <= max);
int count = result.Count();
int inCount = result.Sum(numCount => numCount.Field<int>("COUNT(*)"));
return new Tuple<int, int>(count, inCount);
}

var count = GetCount(datatable, 1, 10);
Console.WriteLine("Belirlenen aralıkta {0} sonuç bulundu, toplam adet {1}.", count.Item1, count.Item2);