鉴于大家对ASP.net十分关注，我们编辑小组在此为大家搜集整理了“ADO.NET中的多数据表操作”一文，供大家参考学习
???????? 在开发基于.NET平台的数据库应用程序时，我们一般都会用到DataSet，作为ADO.NET的核心类它为我们提供了强大的功能，而整个看上去就像是放在内存内的一个小型数据库，内部包括了DataTable、DataView、DataRow、DataColumn、Constraint以及DataRelation。当初看到它时真的是有点兴奋。
???????? 下面根据我的一些经验来举例说明在ADO.NET中的多表填充、关联表更新以及多个Command对象执行过程中启用事务的操作。欢迎大家交流，或在Blog上留言。
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一、准备工作
???????? 对于NorthWind数据库大家都比较熟悉，所以这里拿它为例，我把Customers(客户表)、Orders(订单表)、Order Details(订单详细表)合起来建立了一个类型化的数据集，类型名称为DatasetOrders，每个表只包括一些字段，下面是在Visual Studio .NET中建立的一个截图：
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图1-1
上面建立了两个关系表示为Customers —> Orders —>Order Details。因为Orders表的OrderID字段为自动增长列，这里把就把它的AutoIncrementSeed和AutoIncrementStep值设置成了-1，这在实际添加订单的过程中可能会比较明显，不过不设也没问题。
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二．填充数据集
建立一个窗体程序来演示实际的操作，界面如下：
图2-1
整个应用程序就是一个Form，上面的三个DataGrid分别用来显示相关表的数据，不过他们是互动的。另外的两个单选框用来决定更新数据的方式，两个按钮正如他们的名称来完成相应的功能。
这里我们用一个DataAdapter来完成数据集的填充，执行的存储过程如下：
CREATE PROCEDURE GetCustomerOrdersInfo
AS
SELECT CustomerID,CompanyName,ContactName FROM Customers WHERE CustomerID LIKE ''A%''
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SELECT OrderID,OrderDate,CustomerID FROM Orders? WHERE CustomerID IN
(SELECT CustomerID FROM Customers WHERE CustomerID LIKE ''A%'')
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SELECT OrderID,ProductID,UnitPrice,Quantity,Discount FROM [Order Details] WHERE OrderID IN
(SELECT OrderID FROM Orders? WHERE CustomerID IN
(SELECT CustomerID FROM Customers WHERE CustomerID LIKE ''A%''))
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GO
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为了减少数据量，这里只取了CustomerID以’A’开头的数据。
建立DataAccess类来管理窗体同数据层的交互：
using System;
using System.Data;
using System.Data.SqlClient;
using Microsoft.ApplicationBlocks.Data;
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namespace WinformTest
{
???? public class DataAccess
???? {
???????? private string _connstring = "data source=(local);initial catalog=Northwind;uid=csharp;pwd=c#.net2004;";
???????? private SqlConnection _conn;
???????? ///构造函数
public DataAccess()
???????? {
????????????? _conn = new SqlConnection(_connstring);
}
下面的函数完成单个数据适配器来完成数据集的填充，
public void FillCustomerOrdersInfo(DatasetOrders ds)
???? ???? {
????????????? SqlCommand comm = new SqlCommand("GetCustomerOrdersInfo",_conn);
????????????? comm.CommandType = CommandType.StoredProcedure;
????????????? SqlDataAdapter dataAdapter = new SqlDataAdapter(comm);
????????????? dataAdapter.TableMappings.Add("Table","Customers");
????????????? dataAdapter.TableMappings.Add("Table1","Orders");
????????????? dataAdapter.TableMappings.Add("Table2","Order Details");
????????????? dataAdapter.Fill(ds);
???????? }
如果使用SqlHelper来填充那就更简单了，
???????? public void FillCustomerOrdersInfoWithSqlHelper(DatasetOrders ds)
???????? {???????????? SqlHelper.FillDataset(_connstring,CommandType.StoredProcedure,"GetCustomerOrdersInfo",ds,new string[]{"Customers","Orders","Order Details"});
???????? }
叉开话题提一下，Data Access Application Block 2.0中的SqlHelper.FillDataset这个方法超过两个表的填充时会出现错误，其实里面的逻辑是错的，只不过两个表的时候刚好凑巧，下面是从里面截的代码：
private static void FillDataset(SqlConnection connection, SqlTransaction transaction, CommandType commandType,
????????????? string commandText, DataSet dataSet, string[] tableNames,
????????????? params SqlParameter[] commandParameters)
???????? {
????????????? if( connection == null ) throw new ArgumentNullException( "connection" );
????????????? if( dataSet == null ) throw new ArgumentNullException( "dataSet" );
????????????? SqlCommand command = new SqlCommand();
????????????? bool mustCloseConnection = false;
????????????? PrepareCommand(command, connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection );
??? ????????? using( SqlDataAdapter dataAdapter = new SqlDataAdapter(command) )
????????????? {
???????? ????????? if (tableNames != null && tableNames.Length > 0)
?????????????????? {
?????????????????????? string tableName = "Table";
?????????????????????? for (int index=0; index < tableNames.Length; index++)
?????????????????????? {
??????????????????????????? if( tableNames[index] == null || tableNames[index].Length == 0 )
???????????????????????????????? throw new ArgumentException( "The tableNames parameter must contain a list of tables, a value was provided as null or empty string.", "tableNames" );
??????????????????????????? tableName += (index + 1).ToString();//这里出现错误
?????????????????????? }
?????????????????? }
?????????????????? dataAdapter.Fill(dataSet);
?????????????????? command.Parameters.Clear();
????????????? }
????????????? if( mustCloseConnection )
?????????????????? connection.Close();
???????? }
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这里把tableName += (index + 1).ToString();修改成
dataAdapter.TableMappings.Add((index>0)?(tableName+index.ToString()):tableName, tableNames[index]);就能解决问题。
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接下来看看窗体程序的代码：
public class Form1 : System.Windows.Forms.Form
???? {
???????? private DataAccess _dataAccess;
???????? private DatasetOrders _ds;
???????? //……
???????? //构造函数
???????? public Form1()
???????? {
????????????? InitializeComponent();
????????????? _dataAccess = new DataAccess();
????????????? _ds = new DatasetOrders();
????????????? _ds.EnforceConstraints = false; //关闭约束检查，提高数据填充效率
????????????? this.dataGridCustomers.DataSource = _ds;
????????????? this.dataGridCustomers.DataMember = _ds.Customers.TableName;
????????????? this.dataGridOrders.DataSource = _ds;
????????????? this.dataGridOrders.DataMember = _ds.Customers.TableName+"."+_ds.Customers.ChildRelations[0].RelationName;
????????????? this.dataGridOrderDetails.DataSource = _ds;
????????????? this.dataGridOrderDetails.DataMember = _ds.Customers.TableName+"."+_ds.Customers.ChildRelations[0].RelationName+"."+_ds.Orders.ChildRelations[0].RelationName;
???????? }
对于上面的三个表的动态关联，你也可以使用SetDataBinding方法来完成数据的动态绑定，而不是分别指定DataGride的DataSource和DataMemger属性。
this.dataGridCustomers.SetDataBinding(_ds,_ds.Customers.TableName);
this.dataGridOrders.SetDataBinding(_ds,_ds.Customers.TableName+&q
