DataSet中表示表之间关系

    两表之间存在父子关系，可以使用DataReleation类表示。

    DataRelation对象用于描述DataSet中多个DataTable对象之间的关系。每个DataSet都包含DataRelations的Relations集合，以查找和操纵相关表。

 

如下面代码，得到Customers表中各行中关联子表Orders表中的资料。

using  System.Data.SqlClient;

         string  sConnection  =   " Data Source=scott;Initial Catalog=northwind;Persist Security Info=True;User ID=sa;Password=sa123 " ;
        DataSet dsSet  =   new  DataSet();
        SqlDataAdapter sdaAdapter  =   null ;

         ///   <summary>
         ///  显示表中资料
         ///   </summary>
         private   void  ShowData()
        {
             // 建立Connection
            SqlConnection scConnection  =   new  SqlConnection(sConnection);
             // 建立Customer表Command
            SqlCommand scCommand  =  scConnection.CreateCommand();
            scCommand.CommandText  =   " select * from customers " ;
             // 建立Adapter
            sdaAdapter  =   new  SqlDataAdapter(scCommand);
             // 得到数据
            sdaAdapter.Fill(dsSet,  " customers " );

             // 建立Order表Command
            SqlCommand scOrderCommand  =  scConnection.CreateCommand();
            scOrderCommand.CommandText  =   " select * from Orders " ;
            SqlDataAdapter sdaOrder  =   new  SqlDataAdapter(scOrderCommand);
            sdaOrder.Fill(dsSet,  " orders " );

             // 建立关联

            DataRelation drCustRelection = dsSet.Relations.Add("CustOrders", 

dsSet.Tables["customers"].Columns["CustomerID"], dsSet.Tables["Orders"].Columns["CustomerID"]);

             foreach  (DataRow drCust  in  dsSet.Tables[ " customers " ].Rows)
            {
                DataTable dt  =   null ;
                 // 通过Row.GetChildRows()方法得到子表资料
                 foreach  (DataRow drOrders  in  drCust.GetChildRows(drCustRelection))
                {
                    dt  =  dsSet.Tables[ " orders " ].Clone();
                    DataRow dr  =  dt.NewRow();
                     for  ( int  i  =   0 ; i  <  dsSet.Tables[ " Orders " ].Columns.Count; i ++ )
                    {
                        dr[i]  =  drOrders[i];
                    }
                     // 得到关联表的资料
                    dt.Rows.Add(dr);
                }
            }
        }

 

多表关联例子：

 

using  System.Data;
using  System.Data.SqlClient;

namespace  ManyRelations
{
     class  Program
    {
         static   void  Main( string [] args)
        {
             //  Specify SQL Server-specific connection string

            SqlConnection thisConnection  =   new  SqlConnection(
                  @" Data Source=scott;Initial Catalog=northwind;Persist Security Info=True;User ID=sa;Password=sa123 " );

            DataSet thisDataSet  =   new  DataSet();
            SqlDataAdapter custAdapter  =   new  SqlDataAdapter(
                  " SELECT * FROM Customers " , thisConnection);
            custAdapter.Fill(thisDataSet,  " Customers " );

            SqlDataAdapter orderAdapter  =   new  SqlDataAdapter(
                  " SELECT * FROM Orders " , thisConnection);
            orderAdapter.Fill(thisDataSet,  " Orders " );

            SqlDataAdapter detailAdapter  =   new  SqlDataAdapter(
                  " SELECT * FROM [Order Details] " , thisConnection);
            detailAdapter.Fill(thisDataSet,  " Order Details " );

            SqlDataAdapter prodAdapter  =   new  SqlDataAdapter(
                  " SELECT * FROM Products " , thisConnection);
            prodAdapter.Fill(thisDataSet,  " Products " );

            DataRelation custOrderRel  =  thisDataSet.Relations.Add( " CustOrders " ,
                        thisDataSet.Tables[ " Customers " ].Columns[ " CustomerID " ],
                        thisDataSet.Tables[ " Orders " ].Columns[ " CustomerID " ]);

            DataRelation orderDetailRel  =  thisDataSet.Relations.Add( " OrderDetail " ,
                        thisDataSet.Tables[ " Orders " ].Columns[ " OrderID " ],
                        thisDataSet.Tables[ " Order Details " ].Columns[ " OrderID " ]);

            DataRelation orderProductRel  =  thisDataSet.Relations.Add(
               " OrderProducts " , thisDataSet.Tables[ " Products " ].Columns[ " ProductID " ],
               thisDataSet.Tables[ " Order Details " ].Columns[ " ProductID " ]);

             foreach  (DataRow custRow  in  thisDataSet.Tables[ " Customers " ].Rows)
            {
                Console.WriteLine( " Customer ID:  "   +  custRow[ " CustomerID " ]);

                 foreach  (DataRow orderRow  in  custRow.GetChildRows(custOrderRel))
                {
                    Console.WriteLine( " \tOrder ID:  "   +  orderRow[ " OrderID " ]);
                    Console.WriteLine( " \t\tOrder Date:  "   +  orderRow[ " OrderDate " ]);

                     foreach  (DataRow detailRow  in
                             orderRow.GetChildRows(orderDetailRel))
                    {
                        Console.WriteLine( " \t\tProduct:  "   +
                        detailRow.GetParentRow(orderProductRel)[ " ProductName " ]);
                        Console.WriteLine( " \t\tQuantity:  "   +  detailRow[ " Quantity " ]);
                    }
                }
            }
            thisConnection.Close();
            Console.Write( " Program finished, press Enter/Return to continue: " );
            Console.ReadLine();
        }
    }
}