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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》 Trackback: http://tb.blog.csdn.net/TrackBack.aspx?PostId=67037 |
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