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29.6.4 示例应用程序(2)
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29.6.4 示例应用程序(2)
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2006-10-13 14:41:00
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<div style='float:left;width:49%'>·<a href='100165760.htm'>29.6.2 事务处理的属性</a></div><div style='float:right;width:49%'>·<a href='100165761.htm'>29.6.3 事务处理的结果</a></div><div style='float:left;width:49%'>·<a href='100165762.htm'>29.6.4 示例应用程序(1)</a></div><div style='float:right;width:49%'>·<a href='100165764.htm'>29.7 小结</a></div><div style='float:left;width:49%'>·<a href='100165765.htm'>30.1 管理文件系统</a></div><div style='float:right;width:49%'>·<a href='100165766.htm'>30.1.1 表示文件和文件夹的.NET类</a></div></div>
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<div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /> <h4 style='FTEL:21.45pt'><span lang=EN-US>3. OrderData</span><span
style='font-family:黑体'>组件</span></h4>
<p class=MsoNormal><span lang=ES>OrderData</span><span style='font-family:宋体'>类负责把</span><span
lang=ES>Order</span><span style='font-family:宋体'>对象的值写入数据库。接口</span><span
lang=ES>IOrderUpdate</span><span style='font-family:宋体'>定义了方法</span><span
lang=ES>Insert()</span><span style='font-family:宋体'>。可以扩展这个接口，使之支持</span><span
lang=ES>Update()</span><span style='font-family:宋体'>方法，该方法会更新数据库中已有的项。</span></p>
<p class=MsoNormal><span lang=ES> </span></p>
<p class=2 style='margin-top:8.15pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span lang=ES>using
System;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>using
System.EnterpriseServices;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>using
System.Data;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>using
System.Data.SqlClient;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES> </span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>namespace
Wrox.ProCSharp.EnterpriseServices</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>{</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>
public interface IOrderUpdate</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>
{</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>
void Insert(Order order);</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>
}</span></p>
<p class=MsoNormal><span style='font-family:宋体'>类</span><span lang=ES>OrderData</span><span
style='font-family:宋体'>的属性</span><span lang=ES>[Transaction]</span><span
style='font-family:宋体'>的值是</span><span lang=ES>TransactionOption.Required</span><span
style='font-family:宋体'>。这表示组件在任何情况下都运行在事务处理中。如果事务处理由调用者创建，</span><span lang=ES>OrderData</span><span
style='font-family:宋体'>就使用这个事务处理，否则<span style='letter-spacing:.1pt'>就创建一个事务处理。这里会创建一个新的事务处理，因为调用组件</span></span><span
lang=ES style='letter-spacing:.1pt'>OrderControl</span><span style='font-family:
宋体;letter-spacing:.1pt'>没有事务处理。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>在服务组件中，只能使用默认的构造函数。但是，可以使用组件服务管理工具配置一个发送给组件的构造字符串</span><span
lang=ES>(</span><span style='font-family:宋体'>如图</span><span lang=ES>29-7</span><span
style='font-family:宋体'>所示</span><span lang=ES>)</span><span style='font-family:
宋体'>。选择组件配置的</span><span lang=ES>Activation</span><span style='font-family:
宋体'>选项卡，可以修改构造字符串。在设置属性</span><span lang=ES>[ConstructiuonEnable]</span><span
style='font-family:宋体'>时，选项</span><span lang=ES>Enable object constructiuon</span><span
style='font-family:宋体'>会打开，因为它与类</span><span lang=ES>OrderData</span><span
style='font-family:宋体'>一起使用。</span><span lang=ES>[ConstructiuonEnable]</span><span
style='font-family:宋体'>的属性</span><span lang=ES>Default</span><span
style='font-family:宋体'>定义了默认的连接字符串，在注册程序集后，该字符串会显示在</span><span lang=ES>Activation</span><span
style='font-family:宋体'>设置中。设置这个属性还需要重载基类</span><span lang=ES>ServicedComponent</span><span
style='font-family:宋体'>中的方法</span><span lang=ES>Construct()</span><span
style='font-family:宋体'>。这个方法由</span><span lang=ES>COM+</span><span
style='font-family:宋体'>运行库在对象实例化时调用，同时把构造字符串作为参数传送。构造字符串被设置为变量</span><span
lang=ES>connectionString</span><span style='font-family:宋体'>，该变量在以后用于连接数据库。</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>[Transaction(TransactionOption.Required)]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>[EventTrackingEnabled(true)]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>[ConstructionEnabled(true,
Default="server=localhost;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:55.6pt'><span lang=ES>database=northwind;trusted_connection=true")]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>public
class OrderData : ServicedComponent, IOrderUpdate</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>{</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>
private string connectionString = null;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES> </span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>
protected override void Contruct(string s)</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>
{</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>
connectionString = s;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>
}</span></p>
<p class=MsoNormal><span style='font-family:宋体'>方法</span><span lang=ES>Insert()</span><span
style='font-family:宋体'>是组件的核心。这里使用</span><span lang=ES>ADO.NET</span><span
style='font-family:宋体'>把</span><span lang=ES>Order</span><span
style='font-family:宋体'>对象写入数据库。</span><span lang=ES>ADO.NET</span><span
style='font-family:宋体'>详见第</span><span lang=ES>22</span><span style='font-family:
宋体'>章。对于这个示例，我们创建一个</span><span lang=ES>sqlConnection</span><span
style='font-family:宋体'>对象，在该对象中，使用方法</span><span lang=EN-US>Construct()</span><span
style='font-family:宋体'>设置连接字符串，以初始化该对象。</span></p>
<p align=center><span lang=ES><img width=279 height=309
src="29/image007.jpg"></span></p>
<p align=center style='FTEL:8.15pt'><span style='font-family:宋体'>图</span><span
lang=ES> 29-7</span></p>
<p class=MsoNormal><span style='font-family:宋体'>属性</span><span lang=ES>[AutoComplete()]</span><span
style='font-family:宋体'>应用于下面的方法，进行前面论述的自动事务处理。</span></p>
<p class=2 style='margin-top:8.15pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:27.65pt'><span lang=ES>
[AutoComplete()]</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>
public void Insert(Order order)</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:27.65pt'><span lang=ES>
{</span></p>
<p class=2 style='margin-top:0cm;margin-right:0cm;FTEL:8.15pt;
margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>
SqlConnection connection = new SqlConnection(connectionString);</span></p>
<p class=MsoNormal><span style='font-family:宋体'>方法</span><span lang=ES>connection.CreateCommand()</span><span
style='font-family:宋体'>创建一个</span><span lang=ES>SqlCommand</span><span
style='font-family:宋体'>对象，在该对象中，把</span><span lang=ES>CommandText</span><span
style='font-family:宋体'>属性设置为一个</span><span lang=ES>SQL INSERT</span><span
style='font-family:宋体'>语句，用于把新记录添加到</span><span lang=ES>Orders</span><span
style='font-family:宋体'>表中。方法</span><span lang=ES>ExecuteNonQuery()</span><span
style='font-family:宋体'>执行这个</span><span lang=ES>SQL</span><span
style='font-family:宋体'>语句：</span></p>
<p class=2 style='margin-top:8.15pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span lang=ES>try</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>{</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=ES>
SqlCommand command = connection.CreateCommand();</span></p>
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