ado.net中的多数据表操作浅析—修改
作者：郑佐??????? 2004-8-5
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
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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");
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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");
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_customerdataadapter = new sqldataadapter(selectcustomercomm);
_customerdataadapter.insertcommand = insertcustomercomm;
_customerdataadapter.updatecommand = updatecustomercomm;
_customerdataadapter.deletecommand = deletecustomercomm;
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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
set @orderid = scope_identity()
go
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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");
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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。
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（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();
}
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本文参考：《ado.net core reference》
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