两个DataTable关联查询（inner join、left join）C#代码

 using System;
 using System.Collections.Generic;
 using System.Text;
 using System.Data;

 namespace ConsoleApplication1
 {
     /// <summary>
     /// 在返回的table处大断点查看结果
     /// </summary>
     class Program
     {
         static void Main(string[] args)
         {
             CreatTable();
         }

         /// <summary>
         /// 创建两个测试表
         /// </summary>
         public static void CreatTable()
         {
             //定义数据结构
             DataTable Ks = new DataTable("客商"); //左表or主表
             DataColumn dcID = new DataColumn("ID", System.Type.GetType("System.Int32"));
             DataColumn dcNa = new DataColumn("客商名称", System.Type.GetType("System.String"));
             Ks.Columns.Add(dcID);
             Ks.Columns.Add(dcNa);

             DataTable Dj = new DataTable("订单");//右表or子表
             DataColumn dcID2 = new DataColumn("ID", System.Type.GetType("System.Int32"));
             DataColumn dcNu = new DataColumn("订单数量", System.Type.GetType("System.Int32"));
             Dj.Columns.Add(dcID2);
             Dj.Columns.Add(dcNu);

             //左表数据
             DataRow KsDt = Ks.NewRow();
             KsDt["ID"] = ;
             KsDt["客商名称"] = "张三";
             Ks.Rows.Add(KsDt);

             KsDt = Ks.NewRow();
             KsDt["ID"] = ;
             KsDt["客商名称"] = "李四";
             Ks.Rows.Add(KsDt);

             KsDt = Ks.NewRow();
             KsDt["ID"] = ;
             KsDt["客商名称"] = "王武";
             Ks.Rows.Add(KsDt);

             KsDt = Ks.NewRow();
             KsDt["ID"] = ;
             KsDt["客商名称"] = "赵柳";
             Ks.Rows.Add(KsDt);

             //右表数据
             KsDt = Dj.NewRow();
             KsDt["ID"] = ;
             KsDt["订单数量"] = ;
             Dj.Rows.Add(KsDt);

             //KsDt = Dj.NewRow();
             //KsDt["ID"] = 11;
             //KsDt["订单数量"] = 12;
             //Dj.Rows.Add(KsDt);

             //KsDt = Dj.NewRow();
             //KsDt["ID"] = 12;
             //KsDt["订单数量"] = 16;
             //Dj.Rows.Add(KsDt);

             //KsDt = Dj.NewRow();
             //KsDt["ID"] = 13;
             //KsDt["订单数量"] = 30;
             //Dj.Rows.Add(KsDt);

             KsDt = Dj.NewRow();
             KsDt["ID"] = ;
             KsDt["订单数量"] = ;
             Dj.Rows.Add(KsDt);

             KsDt = Dj.NewRow();
             KsDt["ID"] = ;
             KsDt["订单数量"] = ;
             Dj.Rows.Add(KsDt);

             /*********************调用******************************************/
             //
             Join(Ks, Dj, new DataColumn[] { Ks.Columns["ID"] }, new DataColumn[] { Dj.Columns["ID"] });
             //重载1
             Join(Ks, Dj, Ks.Columns["ID"], Dj.Columns["ID"]);
             //重载2
             Join(Ks, Dj, "ID", "ID");

             /*********************调用结束**************************************/
         }

         /// <summary>
         /// 建立两内存表的链接
         /// </summary>
         /// <param name="dt1">左表（主表）</param>
         /// <param name="dt2">右表</param>
         /// <param name="FJC">左表中关联的字段名（字符串）</param>
         /// <param name="SJC">右表中关联的字段名（字符串）</param>
         /// <returns></returns>
         public static DataTable Join(DataTable dt1, DataTable dt2, DataColumn[] FJC, DataColumn[] SJC)
         {
             //创建一个新的DataTable
             DataTable table = new DataTable("Join");

             // Use a DataSet to leverage DataRelation
             using (DataSet ds = new DataSet())
             {
                 //把DataTable Copy到DataSet中
                 ds.Tables.AddRange(new DataTable[] { dt1.Copy(), dt2.Copy() });

                 DataColumn[] First_columns = new DataColumn[FJC.Length];
                 for (int i = ; i < First_columns.Length; i++)
                 {
                     First_columns[i] = ds.Tables[].Columns[FJC[i].ColumnName];
                 }

                 DataColumn[] Second_columns = new DataColumn[SJC.Length];
                 for (int i = ; i < Second_columns.Length; i++)
                 {
                     Second_columns[i] = ds.Tables[].Columns[SJC[i].ColumnName];
                 }

                 //创建关联
                 DataRelation r = new DataRelation(string.Empty, First_columns, Second_columns, false);
                 ds.Relations.Add(r);

                 //为关联表创建列
                 for (int i = ; i < dt1.Columns.Count; i++)
                 {
                     table.Columns.Add(dt1.Columns[i].ColumnName, dt1.Columns[i].DataType);
                 }

                 for (int i = ; i < dt2.Columns.Count; i++)
                 {
                     //看看有没有重复的列，如果有在第二个DataTable的Column的列明后加_Second
                     if (!table.Columns.Contains(dt2.Columns[i].ColumnName))
                         table.Columns.Add(dt2.Columns[i].ColumnName, dt2.Columns[i].DataType);
                     else
                         table.Columns.Add(dt2.Columns[i].ColumnName + "_Second", dt2.Columns[i].DataType);
                 }

                 table.BeginLoadData();
                 int itable2Colomns = ds.Tables[].Rows[].ItemArray.Length;
                 foreach (DataRow firstrow in ds.Tables[].Rows)
                 {
                     //得到行的数据
                     DataRow[] childrows = firstrow.GetChildRows(r);//第二个表关联的行
                     if (childrows != null && childrows.Length > )
                     {
                         object[] parentarray = firstrow.ItemArray;
                         foreach (DataRow secondrow in childrows)
                         {
                             object[] secondarray = secondrow.ItemArray;
                             object[] joinarray = new object[parentarray.Length + secondarray.Length];
                             Array.Copy(parentarray, , joinarray, , parentarray.Length);
                             Array.Copy(secondarray, , joinarray, parentarray.Length, secondarray.Length);
                             table.LoadDataRow(joinarray, true);
                         }

                     }
                     else//如果有外连接(Left Join)添加这部分代码
                     {
                         object[] table1array = firstrow.ItemArray;//Table1
                         object[] table2array = new object[itable2Colomns];
                         object[] joinarray = new object[table1array.Length + itable2Colomns];
                         Array.Copy(table1array, , joinarray, , table1array.Length);
                         Array.Copy(table2array, , joinarray, table1array.Length, itable2Colomns);
                         table.LoadDataRow(joinarray, true);
                         DataColumn[] dc = new DataColumn[];
                         dc[] = new DataColumn("");
                     }
                 }
                 table.EndLoadData();
             }
             return table;//***在此处打断点，程序运行后点击查看即可观察到结果
         }

         /// <summary>
         /// 重载1
         /// </summary>
         /// <param name="dt1"></param>
         /// <param name="dt2"></param>
         /// <param name="FJC"></param>
         /// <param name="SJC"></param>
         /// <returns></returns>
         public static DataTable Join(DataTable dt1, DataTable dt2, DataColumn FJC, DataColumn SJC)
         {
             return Join(dt1, dt2, new DataColumn[] { FJC }, new DataColumn[] { SJC });
         }

         /// <summary>
         /// 重载2
         /// </summary>
         /// <param name="dt1"></param>
         /// <param name="dt2"></param>
         /// <param name="FJC"></param>
         /// <param name="SJC"></param>
         /// <returns></returns>
         public static DataTable Join(DataTable dt1, DataTable dt2, string FJC, string SJC)
         {
             return Join(dt1, dt2, new DataColumn[] { dt1.Columns[FJC] }, new DataColumn[] { dt1.Columns[SJC] });
         }

     }
 }

上面运行的结果：

这是通过网上整理的，适合处理两个服务器上的数据关联。欢迎留言。