支持XML Web服务的事务利用公共语言运行期中的支持，其是基于Microsoft Transaction Server ( MTS)和COM+ Services中相同的分布式事务模型。该模型基于明确的判断一个对象是否参与一个事务，而不是编写特定的代码用来处理委托和回调一个事务。对于一个使用ASP.NET创建的XML Web服务，你可以通过设置其应用到一个XML Web服务方法上的WebMethod属性的TransactionOption属性来声明一个XML Web服务的事务行为。如果该XML Web服务方法执行的时候抛出一个异常，那么该事务自动地结束；相反，如果没有发生异常，该事务自动委托。
WebMethod属性的TransactionOption属性规定一个XML Web服务方法如何参与一个事务。虽然这个声明级别表示一个事务逻辑，但是它是消除实际事务的一个步骤。当事物对象访问数据源（如数据库或消息队列）时实际事务产生。关联该对象的事务自动流向适当的资源管理程序。像.NET Framework Data Provider（用于SQL Server或OLE DB）这样的.NET Framework数据提供者在对象的上下文中查找事务并通过Distributed Transaction Coordinator (DTC，分布式事务协调程序)编目事务。全部的事务自动产生。
XML Web服务方法只能参与一个作为新事务的根的事务。作为一个新事务的根，所有的与资源管理器（像运行Microsoft SQL Server、Microsoft Message Queuing和Microsoft Host Integration Server的服务器）的相互作用维护需要运行健壮的分布式应用程序的ACID性质。调用其他的XML Web服务方法的XML Web服务方法参与不同的事务，因为事务不流经XML Web服务方法。
使用来自XML Web服务方法的事务
声明一个XML Web服务。
[C#]
<%@ WebService Language="C#" Class="Orders" %>
[Visual Basic]
<%@ WebService Language="VB" Class="Orders" %>
把一个汇编指令加到System.EnterpriseServices上。
<%@ Assembly name="System.EnterpriseServices,Version=1.0.3300.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a" %>
添加引用到System.Web.Services和System.EnterpriseServices域名空间。
[C#]
using System.Web.Services;
using System.EnterpriseServices;
[Visual Basic]
Imports System.Web.Services
Imports System.EnterpriseServices
声明一个XML Web服务方法，设置WebMethod属性的TransactionOption属性为TransactionOption.RequiresNew。
[C#]
[ WebMethod(TransactionOption=TransactionOption.RequiresNew)]
public int DeleteAuthor(string lastName)
[Visual Basic]
< WebMethod(TransactionOption:=TransactionOption.RequiresNew)> _
Public Function DeleteAuthor(lastName As String) As Integer
下面的代码示例显示一个使用单个XML Web服务方法的XML Web服务，调用DeleteDatabase。这个XML Web服务方法执行一个事务范围内的数据库操作。如果该数据库操作抛出一个异常，该事务自动地停止；否则，该事务自动地委托。
[C#]
<%@ WebService Language="C#" Class="Orders" %>
<%@ Assembly name="System.EnterpriseServices,Version=1.0.3300.0,Culture=neutral,PublicKeyToken=b03f5f7f11d50a3a" %>
using System;
using System.Data;
using System.Data.SqlClient;
using System.Web.Services;
using System.EnterpriseServices;
public class Orders : WebService
{
[ WebMethod(TransactionOption=TransactionOption.RequiresNew)]
public int DeleteAuthor(string lastName)
{
String deleteCmd = "DELETE FROM authors WHERE au_lname='" +
lastName + "'" ;
String exceptionCausingCmdSQL = "DELETE FROM NonExistingTable WHERE
au_lname='" + lastName + "'" ;
SqlConnection sqlConn = new SqlConnection(
"Persist Security Info=False;Integrated Security=SSPI;database=pubs;server=myserver");
SqlCommand deleteCmd = new SqlCommand(deleteCmdSQL,sqlConn);
SqlCommand exceptionCausingCmd = new
SqlCommand(exceptionCausingCmdSQL,sqlConn);
// This command should execute properly.
deleteCmd.Connection.Open();
deleteCmd.ExecuteNonQuery();
// This command results in an exception, so the first command is
// automatically rolled back. Since the XML Web service method is
// participating in a transaction, and an exception occurs, ASP.NET
// automatically aborts the transaction. The deleteCmd that
// executed properly is rolled back.
int cmdResult = exceptionCausingCmd.ExecuteNonQuery();
sqlConn.Close();
return cmdResult;
}
}
[Visual Basic]
<%@ WebService Language="VB" Class="Orders" %>
<%@ assembly name="System.EnterpriseServices" %>
Imports System
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web.Services
Imports System.Web.Util
Imports System.EnterpriseServices
Public Class Orders
<WebMethod(TransactionOption:=TransactionOption.RequiresNew)> _
Public Function DeleteAuthor (lastName as String) as Integer
Dim deleteCmdSQL As String = "DELETE FROM authors WHERE au_lname='" + _
lastName + "'"
Dim exceptionCausingCmdSQL As String = "DELETE FROM " + _
"NonExistingTable WHERE au_lname='" + lastName + "'"
Dim sqlConn As SqlConnection = New SqlConnection( _
"Persist Security Info=False;Integrated Security=SSPI;database=pubs;server=myserver")
Dim deleteCmd As SqlCommand = New SqlCommand(deleteCmdSQL,sqlConn)
Dim exceptionCausingCmd As SqlCommand = New _
SqlCommand(exceptionCausingCmdSQL,sqlConn)
' This command should execute properly.
deleteCmd.Connection.Open()
deleteCmd.ExecuteNonQuery()
' This command results in an exception, so the first command is
' automatically rolled back. Since the XML Web service method is
' participating in a transaction, and an exception occurs, ASP.NET
' automatically aborts the transaction. The deleteCmd that
' executed properly is rolled back.
Dim cmdResult As Integer = exceptionCausingCmd.ExecuteNonQuery()
sqlConn.Close()
Return cmdResult
End Function
End Class
