构思：先计算各自的数量，那些数量最多，输出详细信息

 

具体算法如下：

public class Count    {        #region 计算各实体数量        public static Hashtable EntityCount(DataTable dt, string clmnUid)        {            //List
      
        lst = new List
       
        ();            Hashtable uidsCount = new Hashtable();            foreach( DataRow row in dt.Rows)            {                string uid = row[clmnUid].ToString();                if (uidsCount.Contains(uid))                {                    uidsCount[uid] = (int)uidsCount[uid] + 1;                }                else                {                    uidsCount.Add(uid,1);                }            }            return uidsCount;        }        #endregion        #region 获取数量最多的实体        public static IList
        
          MaxCountUid(Hashtable uidsCount,bool listResult)        {            int maxCount = 0;            IList
         
           uids = new List
          
           ();            int value = 0;            foreach (DictionaryEntry kv in uidsCount)            {                value = (int)kv.Value;                if (value > maxCount)                {                    maxCount = value;                    uids.Clear();                    uids.Add(kv.Key.ToString());                }                else if(value == maxCount)                {                    uids.Add(kv.Key.ToString());                }            }            return uids;        }        public static Hashtable MaxCountUid(Hashtable uidsCount)        {            int maxCount = 0;            Hashtable uids = new Hashtable();            int value = 0;            foreach (DictionaryEntry kv in uidsCount)            {                value = (int)kv.Value;                if (value > maxCount)                {                    maxCount = value;                    uids.Clear();                    uids.Add(kv.Key,kv.Value);                }                else if (value == maxCount)                {                    uids.Add(kv.Key, kv.Value);                }            }            return uids;        }        #endregion        #region 输出用户的ID、姓名、数量        public static void PrintMaxCountName(IList
           
             uids,DataTable users, string clmnUid, string clmnName) { foreach(DataRow dr in users.Rows) { string strUid = dr[clmnUid].ToString(); foreach(string uid in uids) { if (uid == strUid) { string strName = dr[clmnName].ToString(); Console.WriteLine(strUid + ":" + strName); } } } } public static void PrintMaxCountName(Hashtable uids, DataTable users, string clmnUid, string clmnName) { foreach (DataRow dr in users.Rows) { string strUid = dr[clmnUid].ToString(); foreach (DictionaryEntry kv in uids) { if (kv.Key.ToString() == strUid) { string strName = dr[clmnName].ToString(); Console.WriteLine(strUid + ":" + strName +"(" + kv.Value.ToString() + ")"); } } } } #endregion }
           
          
         
        
       
      

构造测试数据：

public class Data    {        private string[] usersColumns = { "uid", "name" };        private string[] subjectsColumns = { "title", "uid", "time" };        public DataTable initUsers()        {            DataTable users = new DataTable();            foreach (string columnName in usersColumns)            {                users.Columns.Add(columnName);            }            for (int i = 0; i < 10;i++ )            {                users.Rows.Add("uid"+i,"name"+i);            }            return users;        }        public DataTable initSujects()        {            DataTable subjects = new DataTable();            foreach (string columnName in subjectsColumns)            {                subjects.Columns.Add(columnName);            }            for (int i = 0; i < 123; i++)            {                subjects.Rows.Add("title" + i, "uid" + i % 10,"time" + 1);            }            return subjects;        }    }

测试代码：

class Program    {                static void Main(string[] args)        {            const string clmnUid = "uid";            const string clmnName = "name";            Data data = new Data();            DataTable users = data.initUsers();            DataTable subjects = data.initSujects();            Hashtable uidsCount = Count.EntityCount(subjects, clmnUid);            Hashtable maxCountUids = Count.MaxCountUid(uidsCount);            Count.PrintMaxCountName(maxCountUids,users,clmnUid,clmnName);            Console.Read();        }    }

输出结果：

uid0:name0(13)

uid1:name1(13)

uid2:name2(13)