C#中合并DataTable中重复行

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Collections.Generic;


public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        DataTable dt = new DataTable();
        //DataRow dr = new DataRow();
        dt.Columns.Add("C1");
        dt.Columns.Add("C2");
        dt.Columns.Add("C3");
        dt.Columns.Add("C4");
        dt.Rows.Add(new string[4]{ "A1", "A2", "a" ,"1"});
        dt.Rows.Add(new string[4] { "A1", "A2", "b", "1" });
        dt.Rows.Add(new string[4] { "A1", "A2", "c", "1" });
        dt.Rows.Add(new string[4] { "B1", "B2", "a", "1" });


        CompressTable(dt);
        GridView1.DataSource = dt.DefaultView;
        GridView1.DataBind();


    }
    static void CompressTable(DataTable table)
    {
        Dictionary dict = new Dictionary(); //这个字典用于查找第一第二列相同的项目    
        List removeRows = new List(); //这个List 存储需要删除的重复行          
        foreach (DataRow row in table.Rows)
        {
            string key = row[0].ToString() + ";" + row[1].ToString();
            DataRow row1; 
            if (dict.TryGetValue(key, out row1))
            {                    //如果找到重复的行,将第三列和第一个重复行的第4列合并                    
                if (row1[3] == DBNull.Value)
                {
                    row1[3] = row[3].ToString();
                    row1[2] = row[2].ToString();
                }
                else
                {
                    row1[2] = row1[2].ToString() + ";" + row[2].ToString();
                    row1[3] = int.Parse(row1[3].ToString())+ int.Parse(row[3].ToString());
                } removeRows.Add(row); //将这一行加入要删除的行列表中               
            }
            else
            {
                dict.Add(key, row);
            }
        }            //删除重复的行          
        foreach (DataRow row in removeRows) { table.Rows.Remove(row); }
    }
}

运行效果截图: