在开发基于.NET平台的数据库应用程序时&＃xff0c;我们一般都会用到DataSet&＃xff0c;作为ADO.NET的核心类它为我们提供了强大的功能&＃xff0c;而整个看上去就像是放在内存内的一个小型数据库&＃xff0c;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&＃xff0c;或在Blog上留言。
一、准备工作
对于NorthWind数据库大家都比较熟悉&＃xff0c;所以这里拿它为例&＃xff0c;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&＃xff0c;类型名称为DatasetOrders&＃xff0c;每个表只包括一些字段&＃xff0c;下面是在Visual Studio .NET中建立的一个截图&＃xff1a;
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&＃xff0c;这里把就把它的AutoIncrementSeed和AutoIncrementStep值设置成了-1&＃xff0c;这在实际添加订单的过程中可能会比较明显&＃xff0c;不过不设也没问题。
二&＃xff0e;填充数据集
建立一个窗体程序来演示实际的操作&＃xff0c;界面如下&＃xff1a;
图2-1
整个应用程序就是一个Form&＃xff0c;上面的三个DataGrid分别用来显示相关表的数据&＃xff0c;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&＃xff0c;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&＃xff0c;执行的存储过程如下&＃xff1a;
CREATE PROCEDURE GetCustomerOrdersInfo
AS
SELECT CustomerID,CompanyName,ContactName FROM Customers WHERE CustomerID LIKE &＃39;A%&＃39;
SELECT OrderID,OrderDate,CustomerID FROM Orders WHERE CustomerID IN
(SELECT CustomerID FROM Customers WHERE CustomerID LIKE &＃39;A%&＃39;)
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 &＃39;A%&＃39;))
GO
为了减少数据量&＃xff0c;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&＃xff1a;
using System;
using System.Data;
using System.Data.SqlClient;
using Microsoft.ApplicationBlocks.Data;
namespace WinformTest
{
public class DataAccess
{
private string _connstring &＃61; "data source&＃61;(local);initial catalog&＃61;Northwind;uid&＃61;csharp;pwd&＃61;c#.net2004;";
private SqlConnection _conn;
///构造函数
public DataAccess()
{
_conn &＃61; 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&＃xff0c;
public void FillCustomerOrdersInfo(DatasetOrders ds)
{
SqlCommand comm &＃61; new SqlCommand("GetCustomerOrdersInfo",_conn);
comm.CommandType &＃61; CommandType.StoredProcedure;
SqlDataAdapter dataAdapter &＃61; 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&＃xff0c;
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&＃xff0c;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&＃xff0c;其实里面的逻辑是错的&＃xff0c;只不过两个表的时候刚好凑巧&＃xff0c;下面是从里面截的代码&＃xff1a;
private static void FillDataset(SqlConnection connection, SqlTransaction transaction, CommandType commandType,
string commandText, DataSet dataSet, string[] tableNames,
params SqlParameter[] commandParameters)
{
if( connection &＃61;&＃61; null ) throw new ArgumentNullException( "connection" );
if( dataSet &＃61;&＃61; null ) throw new ArgumentNullException( "dataSet" );
SqlCommand command &＃61; new SqlCommand();
bool mustCloseConnection &＃61; false;
PrepareCommand(command, connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection );
using( SqlDataAdapter dataAdapter &＃61; new SqlDataAdapter(command) )
{
if (tableNames !&＃61; null && tableNames.Length > 0)
{
string tableName &＃61; "Table";
for (int index&＃61;0; index { if( tableNames[index] &＃61;&＃61; null || tableNames[index].Length &＃61;&＃61; 0 ) throw new ArgumentException( "The tableNames parameter must contain a list of tables, a value was provided as null or empty string.", "tableNames" ); tableName &＃43;&＃61; (index &＃43; 1).ToString();//这里出现错误 } } dataAdapter.Fill(dataSet); command.Parameters.Clear(); } if( mustCloseConnection ) connection.Close(); } 这里把tableName &＃43;&＃61; (index &＃43; 1).ToString();修改成 dataAdapter.TableMappings.Add((index>0)?(tableName&＃43;index.ToString()):tableName, tableNames[index]);就能解决问题。 接下来看看窗体程序的代码&＃xff1a; public class Form1 : System.Windows.Forms.Form { private DataAccess _dataAccess; private DatasetOrders _ds; //…… //构造函数 public Form1() { InitializeComponent(); _dataAccess &＃61; new DataAccess(); _ds &＃61; new DatasetOrders(); _ds.EnforceConstraints &＃61; false; //关闭约束检查&＃xff0c;提高数据填充效率 this.dataGridCustomers.DataSource &＃61; _ds; this.dataGridCustomers.DataMember &＃61; _ds.Customers.TableName; this.dataGridOrders.DataSource &＃61; _ds; this.dataGridOrders.DataMember &＃61; _ds.Customers.TableName&＃43;"."&＃43;_ds.Customers.ChildRelations[0].RelationName; this.dataGridOrderDetails.DataSource &＃61; _ds; this.dataGridOrderDetails.DataMember &＃61; _ds.Customers.TableName&＃43;"."&＃43;_ds.Customers.ChildRelations[0].RelationName&＃43;"."&＃43;_ds.Orders.ChildRelations[0].RelationName; } 对于上面的三个表的动态关联&＃xff0c;你也可以使用SetDataBinding方法来完成数据的动态绑定&＃xff0c;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&＃43;"."&＃43;_ds.Customers.ChildRelations[0].RelationName); this.dataGridOrderDetails.SetDataBinding(_ds,_ds.Customers.TableName&＃43;"."&＃43;_ds.Customers.ChildRelations[0].RelationName&＃43;"."&＃43;_ds.Orders.ChildRelations[0].RelationName); } 数据填充事件处理如下&＃xff1a; private void buttonFillData_Click(object sender, System.EventArgs e) { _ds.Clear();//重新填充数据集 _dataAccess.FillCustomerOrdersInfo(_ds); //_dataAccess.FillCustomerOrdersInfoWithSqlHelper(_ds); } 执行上面的事件处理函数我们会看到数据显示到对应的DataGrid上&＃xff0c;如(图2-1)所示。 如果使用数据读取器获取多表纪录下面是实现的一种方式(参考)&＃xff1a; SqlCommand comm &＃61; new SqlCommand("GetCustomerOrdersInfo",_conn); comm.CommandType &＃61; CommandType.StoredProcedure; _conn.Open(); SqlDataReader reader &＃61; comm.ExecuteReader(); do { while(reader.Read()) { Console.WriteLine(reader[0].ToString());//获取数据代码 } }while(reader.NextResult()); Console.ReadLine(); _conn.Close(); 三、更新数据集 在DataAccess类中增加两个类成员变量&＃xff1a; private SqlDataAdapter _customerDataAdapter; //客户数据适配器 private SqlDataAdapter _orderDataAdapter; //订单数据适配器 customerDataAdapter在构造函数中的初始化为 //实例化_customerDataAdapter SqlCommand selectCustomerComm &＃61; new SqlCommand("GetCustomer",_conn); selectCustomerComm.CommandType &＃61; CommandType.StoredProcedure; selectCustomerComm.Parameters.Add("&＃64;CustomerID",SqlDbType.NChar,5,"CustomerID"); SqlCommand insertCustomerComm &＃61; new SqlCommand("AddCustomer",_conn); insertCustomerComm.CommandType &＃61; CommandType.StoredProcedure; insertCustomerComm.Parameters.Add("&＃64;CustomerID",SqlDbType.NChar,5,"CustomerID"); insertCustomerComm.Parameters.Add("&＃64;CompanyName",SqlDbType.NVarChar,40,"CompanyName"); insertCustomerComm.Parameters.Add("&＃64;ContactName",SqlDbType.NVarChar,30,"ContactName"); SqlCommand updateCustomerComm &＃61; new SqlCommand("UpdateCustomer",_conn); updateCustomerComm.CommandType &＃61; CommandType.StoredProcedure; updateCustomerComm.Parameters.Add("&＃64;CustomerID",SqlDbType.NChar,5,"CustomerID"); updateCustomerComm.Parameters.Add("&＃64;CompanyName",SqlDbType.NVarChar,40,"CompanyName"); updateCustomerComm.Parameters.Add("&＃64;ContactName",SqlDbType.NVarChar,30,"ContactName"); SqlCommand deleteCustomerComm &＃61; new SqlCommand("DeleteCustomer",_conn); deleteCustomerComm.CommandType &＃61; CommandType.StoredProcedure; deleteCustomerComm.Parameters.Add("&＃64;CustomerID",SqlDbType.NChar,5,"CustomerID"); _customerDataAdapter &＃61; new SqlDataAdapter(selectCustomerComm); _customerDataAdapter.InsertCommand &＃61; insertCustomerComm; _customerDataAdapter.UpdateCommand &＃61; updateCustomerComm; _customerDataAdapter.DeleteCommand &＃61; deleteCustomerComm; 上面的代码完全可以用设计器生成&＃xff0c;觉得有些东西自己写感觉更好&＃xff0c;不过代码还是很多。 对于_orderDataAdapter的初始化同上面的差不多&＃xff0c;这里我们只看订单增加的处理&＃xff0c;下面是存储过程&＃xff1a; CREATE PROCEDURE AddOrder ( &＃64;OrderID INT OUT, &＃64;CustomerID NCHAR(5), &＃64;OrderDate DATETIME ) AS INSERT INTO Orders ( CustomerID , OrderDate ) VALUES ( &＃64;CustomerID , &＃64;OrderDate ) --SELECT &＃64;OrderID &＃61; &＃64;&＃64;IDENTITY //使用触发器有可能出现问题 SET &＃64;OrderID &＃61; SCOPE_IDENTITY() GO OrderID自动增长值的获取通过输出参数来完成&＃xff0c;这个相当不错&＃xff0c;如果使用SqlDataAdapter.RowUpdated事件来处理那效率会很低。 对insertOrderComm对象的定义为&＃xff1a; SqlCommand insertOrderComm &＃61; new SqlCommand("AddOrder",_conn); insertOrderComm.CommandType &＃61; CommandType.StoredProcedure; insertOrderComm.Parameters.Add("&＃64;OrderID",SqlDbType.Int,4,"OrderID"); insertOrderComm.Parameters["&＃64;OrderID"].Direction &＃61; ParameterDirection.Output; insertOrderComm.Parameters.Add("&＃64;OrderDate",SqlDbType.DateTime,8,"OrderDate"); insertOrderComm.Parameters.Add("&＃64;CustomerID",SqlDbType.NChar,5,"CustomerID"); 在实现数据的更新方法之前我们先来明确一些更新逻辑&＃xff1a; 对于标记为删除的行&＃xff0c;先删除订单表的数据&＃xff0c;再删除客户表的数据&＃xff1b; 对于标记为添加的行&＃xff0c;先添加客户表的数据&＃xff0c;再添加订单表的数据。 (1)实现用获取修改过的DataSet的副本子集来更新数据的方法。 这也是调用Xml Web Service更新数据的常用方法&＃xff0c;先来看第一个版本&＃xff0c;子集的获取通过DataSet.GetChangs方法来完成。 //使用数据集子集更新数据 public void UpdateCustomerOrders(DatasetOrders ds) { DataSet dsModified &＃61; ds.GetChanges(DataRowState.Modified);//获取修改过的行 DataSet dsDeleted &＃61; ds.GetChanges(DataRowState.Deleted);//获取标记为删除的行 DataSet dsAdded &＃61; ds.GetChanges(DataRowState.Added);//获取增加的行 try { _conn.Open();//先添加客户表数据&＃xff0c;再添加订单表数据 if(dsAdded !&＃61; null) { _customerDataAdapter.Update(dsAdded,"Customers"); _orderDataAdapter.Update(dsAdded,"Orders"); ds.Merge(dsAdded); } if(dsModified !&＃61; null)//更新数据表 { _customerDataAdapter.Update(dsModified,"Customers"); _orderDataAdapter.Update(dsModified,"Orders"); ds.Merge(dsModified); } if(dsDeleted !&＃61; null)//先删除订单表数据&＃xff0c;再删除客户表数据 { _orderDataAdapter.Update(dsDeleted,"Orders"); _customerDataAdapter.Update(dsDeleted,"Customers"); ds.Merge(dsDeleted); } } catch(Exception ex) { throw new Exception("更新数据出错",ex); } finally { if(_conn.State !&＃61; ConnectionState.Closed) _conn.Close(); } } 上面的方法看上去比较清晰&＃xff0c;不过效率不会很高&＃xff0c;至少中间创建了三个DataSet&＃xff0c;然后又进行了多次合并。 (2)另一方法就是引用更新&＃xff0c;不创建副本。 相对来说性能会高许多&＃xff0c;但是如果用在Web服务上传输的数据量会更大(可以结合两个方法进行改进)。具体的实现就是通过DataTable.Select方法选择行状态来实现。 //引用方式更新数据 public void UpdateCustomerOrders(DataSet ds) { try { _conn.Open(); //先添加客户表数据&＃xff0c;再添加订单表数据 _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Added)); _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Added)); //更新数据表 _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.ModifiedCurrent)); _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.ModifiedCurrent)); //先删除订单表数据&＃xff0c;再删除客户表数据 _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Deleted)); _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Deleted)); } catch(Exception ex) { throw new Exception("更新数据出错",ex); } finally { if(_conn.State !&＃61; ConnectionState.Closed) _conn.Close(); } } 结合上面的两个方法我们可想到调用Web Service有更合理的方法来完成。 (3)使用事务 public void UpdateCustomerOrdersWithTransaction(DataSet ds) { SqlTransaction trans &＃61; null; try { _conn.Open(); trans &＃61; _conn.BeginTransaction(); _customerDataAdapter.DeleteCommand.Transaction &＃61; trans; _customerDataAdapter.InsertCommand.Transaction &＃61; trans; _customerDataAdapter.UpdateCommand.Transaction &＃61; trans; _orderDataAdapter.DeleteCommand.Transaction &＃61; trans; _orderDataAdapter.InsertCommand.Transaction &＃61; trans; _orderDataAdapter.UpdateCommand.Transaction &＃61; trans; _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Added)); _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Added)); _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.ModifiedCurrent)); _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.ModifiedCurrent)); _orderDataAdapter.Update(ds.Tables["Orders"].Select("","",DataViewRowState.Deleted)); _customerDataAdapter.Update(ds.Tables["Customers"].Select("","",DataViewRowState.Deleted)); trans.Commit(); } catch(Exception ex) { trans.Rollback(); throw new Exception("更新数据出错",ex); } finally { if(_conn.State !&＃61; ConnectionState.Closed) _conn.Close(); } } 最后让我们来看看窗体的按钮更新事件的代码&＃xff1a; private void buttonUpdate_Click(object sender, System.EventArgs e) { //提交编辑数据 this.BindingContext[this._ds].EndCurrentEdit(); if(radioButtonRef.Checked &＃61;&＃61; true)//引用方式更新 _dataAccess.UpdateCustomerOrders((DataSet)_ds); else if(radioButtonTrans.Checked &＃61;&＃61; true)//启用事务更新数据表 _dataAccess.UpdateCustomerOrdersWithTransaction((DataSet)_ds); else { DatasetOrders changedData &＃61; (DatasetOrders)_ds.GetChanges(); if(radioButtonWeb.Checked &＃61;&＃61; true)//Web服务的更正更新 { _dataAccess.UpdateCustomerOrders((DataSet)changedData); } else//创建副本合并方式更新 { _dataAccess.UpdateCustomerOrders(changedData); } //去除订单表中添加的虚拟行 foreach(DataRow row in _ds.Orders.Select("","",DataViewRowState.Added)) _ds.Orders.RemoveOrdersRow((DatasetOrders.OrdersRow)row); //去除客户表中添加的虚拟行 foreach(DataRow row in _ds.Customers.Select("","",DataViewRowState.Added)) _ds.Customers.RemoveCustomersRow((DatasetOrders.CustomersRow)row); _ds.Merge(changedData); } //提交数据集状态 _ds.AcceptChanges();
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