获取DataTable的前N行数据然后按指定字段排序

可以使用以下三种代码：

第一种：使用Linq

DataTable dtLast = dataTable.AsEnumerable().Take(count).OrderBy(dataRow => Convert.ToInt32(dataRow["Sequence"])).CopyToDataTable();

第二种：使用默认视图的Sort属性：

            DataTable dtLast = dataTable.AsEnumerable().Take(count).CopyToDataTable();
            dtLast.DefaultView.Sort = "Sequence asc";//逆序为Sequence desc
            dtLast = dtLast.DefaultView.ToTable();

第三种：使用循环迭代

            DataTable dtLast = dataTable.Clone();//克隆表结构，行数为0
            for (int i = 0; i < getCount; i++)
            {
                dtLast.Rows.Add(dataTable.Rows[i].ItemArray);
            }
            //按照Sequence进行排序
            DataRow[] array = dtLast.Select("1=1", "Sequence");
            dtLast = array.CopyToDataTable();

整体测试程序如下：

控制台应用程序FilterDataTableDemo

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FilterDataTableDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            int topCount = 5;
            DataTable dataTable = GetDataTable();
            PrintDataTable(dataTable);
            Console.WriteLine($"----------【使用Linq】打印DataTable的前【{topCount}】行并按Sequence顺序排序----------");
            DataTable dtLinq = GetTopDataAndOrderUseLinq(dataTable, topCount);
            PrintDataTable(dtLinq);
            Console.WriteLine($"--------【使用视图View】打印DataTable的前【{topCount}】行并按Sequence顺序排序--------");
            DataTable dtView = GetTopDataAndOrderUseView(dataTable, topCount);
            PrintDataTable(dtView);
            Console.WriteLine($"--------【使用循环迭代】打印DataTable的前【{topCount}】行并按Sequence顺序排序--------");
            DataTable dtIterator = GetTopDataAndOrderUseIterator(dataTable, topCount);
            PrintDataTable(dtIterator);

            Console.ReadLine();
        }

        /// <summary>
        /// 使用Linq获取前N行数据并排序
        /// </summary>
        /// <param name="dataTable"></param>
        /// <param name="count"></param>
        /// <returns></returns>
        static DataTable GetTopDataAndOrderUseLinq(DataTable dataTable, int count) 
        {
            DataTable dtLast = dataTable.AsEnumerable().Take(count).OrderBy(dataRow => Convert.ToInt32(dataRow["Sequence"])).CopyToDataTable();
            return dtLast;
        }

        /// <summary>
        /// 使用视图的默认排序
        /// </summary>
        /// <param name="dataTable"></param>
        /// <param name="count"></param>
        /// <returns></returns>
        static DataTable GetTopDataAndOrderUseView(DataTable dataTable, int count)
        {
            DataTable dtLast = dataTable.AsEnumerable().Take(count).CopyToDataTable();
            dtLast.DefaultView.Sort = "Sequence asc";//逆序为Sequence desc
            dtLast = dtLast.DefaultView.ToTable();
            return dtLast;
        }

        /// <summary>
        /// 使用循环迭代获取前N行数据并排序
        /// </summary>
        /// <param name="dataTable"></param>
        /// <param name="count"></param>
        /// <returns></returns>
        static DataTable GetTopDataAndOrderUseIterator(DataTable dataTable, int count)
        {
            //考虑到 获取的行数比数据表本身的行数还要多，这里取较小值
            int getCount = Math.Min(dataTable.Rows.Count, count);
            DataTable dtLast = dataTable.Clone();//克隆表结构，行数为0
            for (int i = 0; i < getCount; i++)
            {
                dtLast.Rows.Add(dataTable.Rows[i].ItemArray);
            }
            //按照Sequence进行排序
            DataRow[] array = dtLast.Select("1=1", "Sequence");
            dtLast = array.CopyToDataTable();
            return dtLast;
        }

        /// <summary>
        /// 生成测试内存表
        /// </summary>
        /// <returns></returns>
        static DataTable GetDataTable() 
        {
            DataTable dt = new DataTable("Test");
            dt.Columns.Add("CoreId", typeof(int));
            dt.Columns.Add("Sequence", typeof(int));
            dt.Columns.Add("TestName", typeof(string));

            dt.Rows.Add(10, 5, "云天河");
            dt.Rows.Add(9, 4, "柳梦璃");
            dt.Rows.Add(8, 3, "韩菱纱");
            dt.Rows.Add(7, 2, "慕容紫英");
            dt.Rows.Add(6, 1, "璇玑");
            dt.Rows.Add(5, 5, "怀朔");
            dt.Rows.Add(4, 4, "云天青");
            dt.Rows.Add(3, 3, "夙玉");
            dt.Rows.Add(2, 2, "夙瑶");
            dt.Rows.Add(1, 1, "玄霄");
            return dt;
        }

        /// <summary>
        /// 打印内存数据表信息
        /// </summary>
        /// <param name="dataTable"></param>
        static void PrintDataTable(DataTable dataTable) 
        {
            for (int i = 0; i < dataTable.Rows.Count; i++)
            {
                Console.WriteLine(string.Join(",", dataTable.Rows[i].ItemArray));
            }
        }
    }
}

程序运行如图：