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。
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();
}