事务是一种将活动涉及的所有操作作为一个不可分割的执行单元，所有操作只有在正常执行的情况下方能提交，不然集体回滚。（All or Nothing）
事务具有ACID四种属性：原子性、一致性、隔离性、持久性。
事务的处理方式存在很多种处理方式：
可以居于数据库的存储过程编写SQL事务，或通过ADO.NET、企业库均提供事务。
1、数据库存储过程事务：
数据库结构：
View Code CREATE TABLE [ dbo ]. [ Player_Account ]( [ AccountIPlayer_Account_ID ] [ int ] IDENTITY( 1, 1) NOT NULL, [ PlayerID ] [ int ] NOT NULL, [ AccountName ] [ varchar ]( 30) NOT NULL, [ Password ] [ varchar ]( 30) NOT NULL, [ Balance ] [ decimal ]( 18, 0) NOT NULL, [ Status ] [ int ] NOT NULL, [ ActiveTime ] [ datetime ] NOT NULL, [ CreateTime ] [ datetime ] NOT NULL, [ Remark ] [ varchar ]( 100) NULL, [ ModifyTime ] [ datetime ] NULL, [ ModifyBy ] [ varchar ]( 30) NULL, CONSTRAINT [ PK_PLAYER_ACCOUNT ] PRIMARY KEY CLUSTERED ( [ AccountIPlayer_Account_ID ] ASC ) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [ PRIMARY ] ) ON [ PRIMARY ] CREATE TABLE [ dbo ]. [ Member_Account ]( [ Member_Account_ID ] [ int ] IDENTITY( 1, 1) NOT NULL, [ MemberID ] [ int ] NOT NULL, [ AccountName ] [ varchar ]( 30) NOT NULL, [ Password ] [ varchar ]( 30) NOT NULL, [ Balance ] [ decimal ]( 18, 0) NOT NULL, [ Status ] [ int ] NOT NULL, [ ActiveTime ] [ datetime ] NOT NULL, [ CreateTime ] [ datetime ] NOT NULL, [ Remark ] [ varchar ]( 100) NULL, [ ModifyTime ] [ datetime ] NULL, [ ModifyBy ] [ varchar ]( 30) NULL ) ON [ PRIMARY ]
两个账户的转账是一种复合操作，同时也涉及到事务操作。（当然如果涉及到信用额度、可用额度、状态将更加复杂）
存储过程：
View Code SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO -- 账号转账 CREATE PROCEDURE [ dbo ]. [ Transfer2Player ] @AccountIPlayer_Account_ID INT = NULL, @Member_Account_ID INT = NULL, @Amount DECIMAL = 0 AS BEGIN IF NOT EXISTS( SELECT * FROM Player_Account pa WHERE pa.AccountIPlayer_Account_ID = @AccountIPlayer_Account_ID) BEGIN RAISERROR( ' AccountNotExists ', 16, 1) RETURN END IF NOT EXISTS( SELECT * FROM Member_Account ma WHERE ma.Member_Account_ID = @Member_Account_ID) BEGIN RAISERROR( ' AccountNotExists ', 16, 1) RETURN END IF NOT EXISTS( SELECT * FROM Member_Account ma WHERE ma.Member_Account_ID = @Member_Account_ID AND ma.Balance < @Amount) BEGIN RAISERROR( ' NoEnoughAmount ', 16, 1) RETURN END -- 开始事务 BEGIN TRANSACTION UPDATE Member_Account SET Balance = @Amount WHERE Member_Account_ID = @Member_Account_ID IF @@ERROR <> 0 BEGIN -- 出错回滚 ROLLBACK TRANSACTION END UPDATE Player_Account SET Balance = @Amount WHERE AccountIPlayer_Account_ID = @AccountIPlayer_Account_ID IF @@ERROR <> 0 BEGIN ROLLBACK TRANSACTION END -- 提交事务 COMMIT TRANSACTION END GO
2、ADO.Net 事务
在System.Data.SqlClient也提供了事务功能
View Code private const string connectionString = "server =.; database =Game -Pay2012;sa =sa;pwd = 123456;"; public void Tranfer2Player( int Player_Account_ID, int Member_Account_ID, decimal Amount) { SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings [ connectionString ].ConnectionString); SqlCommand cmd = new SqlCommand(); try { conn. Open(); cmd. Transaction = conn.BeginTransaction(IsolationLevel.RepeatableRead, "Tranfer2PlayerTransaction"); //充值到玩家 cmd.CommandText = " UPDATE Player_Account SET Balance = @Amount WHERE AccountIPlayer_Account_ID = @AccountIPlayer_Account_ID"; cmd.CommandType = CommandType. Text; cmd.Connection = conn; SqlParameter [] paras = new SqlParameter []{ new SqlParameter(" @AccountIPlayer_Account_ID",SqlDbType. Int, 32), new SqlParameter(" @Amount",SqlDbType. Decimal, 18) }; paras [ 0 ].Value = Player_Account_ID; paras [ 1 ].Value = Amount; foreach (SqlParameter para in paras) { cmd.Parameters. Add(para); } cmd.ExecuteNonQuery(); //扣除账号金额 cmd.CommandText = " UPDATE Member_Account SET Balance = @Amount WHERE Member_Account_ID = @Member_Account_ID "; cmd.CommandType = CommandType. Text; cmd.Connection = conn; SqlParameter [] paras2 = new SqlParameter []{ new SqlParameter(" @Member_Account_ID",SqlDbType. Int, 32), new SqlParameter(" @Amount",SqlDbType. Decimal, 18) }; paras [ 0 ].Value = Member_Account_ID; paras [ 1 ].Value = Amount; foreach (SqlParameter para in paras) { cmd.Parameters. Add(para); } cmd.ExecuteNonQuery(); //提交事务 cmd. Transaction. Commit(); } catch (Exception) { //回滚事务 cmd. Transaction. Rollback(); throw; } finally { conn. Close(); } }
出来ADO.Net 像企业库、Linq to Sql也提供了相关的事务。
3、分布式事务
TransactionScope 此类在.Net Framework 2.0 版新增的。它为数据库提供了一个“轻量级”（区别于SqlTransaction）的事务。
在通过 new 语句实例化 TransactionScope 时，事务管理器将确定要参与哪个事务。一经确定，此范围将始终参与该事务。此决策基于两个因素：是否存在环境事务以及构造函数中TransactionScopeOption 参数的值。环境事务是在其中执行您的代码的事务。通过调用 Transaction 类的 Current 静态属性可获取对环境事务的引用。详细请看MSDN：
View Code public class TransactionClass { private const string strcon1 = " Data Source=192.168.1.36;Initial Catalog=TransactionDB;user id=sa;Password=XhTeam; "; private const string strcon2 = " Data Source=192.168.1.36;Initial Catalog=Transaction2DB;user id=sa;Password=XhTeam; "; private const string strcom1 = " INSERT INTO Account(name,password)VALUES('test222','testone') "; private const string strcom2 = " INSERT INTO Logger(title,test)VALUES('testlog222','testonecontent') "; public void CreateTransactionScope() { TransactionOptions tOps = new TransactionOptions(); tOps.IsolationLevel = IsolationLevel.RepeatableRead; tOps.Timeout = new TimeSpan( 0, 3, 0); try { using (TransactionScope scope = new TransactionScope(TransactionScopeOption.RequiresNew,tOps)) { using (SqlConnection con1 = new SqlConnection(strcon1)) { con1.Open(); SqlCommand com1 = new SqlCommand(strcom1, con1); com1.ExecuteNonQuery(); } using (SqlConnection con2 = new SqlConnection(strcon2)) { con2.Open(); SqlCommand com2 = new SqlCommand(strcom2, con2); com2.ExecuteNonQuery(); } scope.Complete(); } } catch (Exception ex) { Console.WriteLine( " 异常信息: " + ex.Message); } } } }
TransactionScope 有三种模式：
TransactionScopeOptions：Required、RequiresNew、Suppress
Required 如果已经存在一个事务，那么这个事务范围将加入已有事务，否则创建自己的事务。
RequiresNew 事务范围将创建自己的事务
Suppress 如果处于当前事务范围，那么事务范围既不会加入范围事务，也不会创建自己的事务。当部分代码留在事务外部时，可以使用该项。