ADO.NET中的多数据表操作浅析—修改

http://blog.csdn.net/zhzuo/archive/2004/08/06/67037.aspx


三、更新数据集

首先需要说明的是我这里去掉了Order Details表，对两个表的操作只是其中的几个字段。下面是窗体界面：






图3-1

单选框用来选择不同的更新方法。

在DataAccess类中增加两个类成员变量：

     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 = new SqlCommand("GetCustomer",_conn);

selectCustomerComm.CommandType = CommandType.StoredProcedure;

selectCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");

        

SqlCommand insertCustomerComm = new SqlCommand("AddCustomer",_conn);

insertCustomerComm.CommandType = CommandType.StoredProcedure;

insertCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");

insertCustomerComm.Parameters.Add("@CompanyName",SqlDbType.NVarChar,40,"CompanyName");

insertCustomerComm.Parameters.Add("@ContactName",SqlDbType.NVarChar,30,"ContactName");



SqlCommand updateCustomerComm = new SqlCommand("UpdateCustomer",_conn);

updateCustomerComm.CommandType = CommandType.StoredProcedure;

updateCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");

updateCustomerComm.Parameters.Add("@CompanyName",SqlDbType.NVarChar,40,"CompanyName");

updateCustomerComm.Parameters.Add("@ContactName",SqlDbType.NVarChar,30,"ContactName");

             

SqlCommand deleteCustomerComm = new SqlCommand("DeleteCustomer",_conn);

deleteCustomerComm.CommandType = CommandType.StoredProcedure;

deleteCustomerComm.Parameters.Add("@CustomerID",SqlDbType.NChar,5,"CustomerID");



_customerDataAdapter = new SqlDataAdapter(selectCustomerComm);

_customerDataAdapter.InsertCommand = insertCustomerComm;

_customerDataAdapter.UpdateCommand = updateCustomerComm;

_customerDataAdapter.DeleteCommand = deleteCustomerComm;



上面的代码完全可以用设计器生成，觉得有些东西自己写感觉更好，不过代码还是很多。

对于_orderDataAdapter的初始化同上面的差不多，这里我们只看订单增加的处理，下面是存储过程：

CREATE PROCEDURE  AddOrder

(

     @OrderID INT OUT,

     @CustomerID NCHAR(5),

     @OrderDate DATETIME

)

AS

INSERT INTO Orders

(

     CustomerID ,

     OrderDate

)

VALUES

(

     @CustomerID ,

     @OrderDate

)

--SELECT @OrderID = @@IDENTITY  //使用触发器有可能出现问题

SET @OrderID = SCOPE_IDENTITY()

GO



OrderID自动增长值的获取通过输出参数来完成，这个相当不错，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：

SqlCommand insertOrderComm = new SqlCommand("AddOrder",_conn);

insertOrderComm.CommandType = CommandType.StoredProcedure;

insertOrderComm.Parameters.Add("@OrderID",SqlDbType.Int,4,"OrderID");

insertOrderComm.Parameters["@OrderID"].Direction = ParameterDirection.Output;

insertOrderComm.Parameters.Add("@OrderDate",SqlDbType.DateTime,8,"OrderDate");

insertOrderComm.Parameters.Add("@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：

对于标记为删除的行，先删除订单表的数据，再删除客户表的数据；

对于标记为添加的行，先添加客户表的数据，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，先来看第一个版本，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 = ds.GetChanges(DataRowState.Modified);//获取修改过的行

     DataSet dsDeleted = ds.GetChanges(DataRowState.Deleted);//获取标记为删除的行

     DataSet dsAdded = ds.GetChanges(DataRowState.Added);//获取增加的行

     try

     {   

         _conn.Open();//先添加客户表数据，再添加订单表数据

         if(dsAdded != null)

         {

              _customerDataAdapter.Update(dsAdded,"Customers");

              _orderDataAdapter.Update(dsAdded,"Orders");

              ds.Merge(dsAdded);

         }

         if(dsModified != null)//更新数据表

         {

              _customerDataAdapter.Update(dsModified,"Customers");

              _orderDataAdapter.Update(dsModified,"Orders");

              ds.Merge(dsModified);

         }

         if(dsDeleted != null)//先删除订单表数据，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 != ConnectionState.Closed)

              _conn.Close();

     }

}

上面的方法看上去比较清晰，不过效率不会很高，至少中间创建了三个DataSet，然后又进行了多次合并。

（2）另一方法就是引用更新，不创建副本。

相对来说性能会高许多，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，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，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 != 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 = null;

     try

     {   

         _conn.Open();

         trans = _conn.BeginTransaction();

         _customerDataAdapter.DeleteCommand.Transaction = trans;

         _customerDataAdapter.InsertCommand.Transaction = trans;

         _customerDataAdapter.UpdateCommand.Transaction = trans;

         _orderDataAdapter.DeleteCommand.Transaction = trans;

         _orderDataAdapter.InsertCommand.Transaction = trans;

         _orderDataAdapter.UpdateCommand.Transaction = 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 != ConnectionState.Closed)

              _conn.Close();

     }

}

最后让我们来看看窗体的按钮更新事件的代码：

private void buttonUpdate_Click(object sender, System.EventArgs e)

{

              //提交编辑数据

     this.BindingContext[this._ds].EndCurrentEdit();

    

     if(radioButtonRef.Checked == true)//引用方式更新

         _dataAccess.UpdateCustomerOrders((DataSet)_ds);

     else if(radioButtonTrans.Checked == true)//启用事务更新数据表

         _dataAccess.UpdateCustomerOrdersWithTransaction((DataSet)_ds);

     else

     {

         DatasetOrders changedData =  (DatasetOrders)_ds.GetChanges();

         if(radioButtonWeb.Checked == 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();

}



本文参考：《ADO.NET Core Reference》