TransactionScope和Enterprise Libray 3.0 Data Access Application Block

2007-04-07 17:38:00

　标签：TransactionScope Access Enterprise Application Block　　　[推送到技术圈]

Enterprise Libray 3.0已经发布了,具体可参见TerryLee的 Enterprise Library 3.0 发布.下载了看看,有非常激动人心的更新.我只是看看Data Access Application Block代码,代码中有这个类TransactionScopeConnections,是个内部类,设计意图很明显就是使用数据库的事务模型.我觉得设计为内部类有点瑕疵,我的习惯是事务和提交在业务逻辑层. .NET 2.0的System.Transactions应该是一个更好的选择。就将Data Access Application Block的QuickStart例子代码：

/// <summary>
/// Transfers an amount between two accounts.
/// </summary>
/// <param name="transactionAmount">Amount to transfer.</param>
/// <param name="sourceAccount">Account to be credited.</param>
/// <param name="destinationAccount">Account to be debited.</param>
/// <returns>true if sucessful; otherwise false.</returns>
/// <remarks>Demonstrates executing multiple updates within the
/// context of a transaction.</remarks>
public bool Transfer(int transactionAmount, int sourceAccount, int destinationAccount)
{
bool result = false;

// Create the Database object, using the default database service. The
// default database service is determined through configuration.
Database db = DatabaseFactory.CreateDatabase();

// Two operations, one to credit an account, and one to debit another
// account.
string sqlCommand = "CreditAccount"
DbCommand creditCommand = db.GetStoredProcCommand(sqlCommand);

db.AddInParameter(creditCommand, "AccountID", DbType.Int32, sourceAccount);
db.AddInParameter(creditCommand, "Amount", DbType.Int32, transactionAmount);

sqlCommand = "DebitAccount"
DbCommand debitCommand = db.GetStoredProcCommand(sqlCommand);

db.AddInParameter(debitCommand, "AccountID", DbType.Int32, destinationAccount);
db.AddInParameter(debitCommand, "Amount", DbType.Int32, transactionAmount);

using (DbConnection connection = db.CreateConnection())
{
connection.Open();
DbTransaction transaction = connection.BeginTransaction();

try
{
// Credit the first account
db.ExecuteNonQuery(creditCommand, transaction);
// Debit the second account
db.ExecuteNonQuery(debitCommand, transaction);

// Commit the transaction
transaction.Commit();

result = true;
}
catch
{
// Rollback transaction
transaction.Rollback();
}
connection.Close();

return result;
}
}

按照TransactionScope类进行改造，试验成功了，代码如下：

public bool Transfer(int transactionAmount, int sourceAccount, int destinationAccount)
{
bool result = false;
Database database = DatabaseFactory.CreateDatabase();

using (TransactionScope scope = new TransactionScope(TransactionScopeOption.RequiresNew))
{
TestCommand1(database, transactionAmount, sourceAccount);
TestCommand2(database, transactionAmount, destinationAccount);
scope.Complete();
result = true;
}
return result;

}

private void TestCommand1(Database db, int transactionAmount, int sourceAccount)
{
string sqlCommand = "CreditAccount"
DbCommand creditCommand = db.GetStoredProcCommand(sqlCommand);

db.AddInParameter(creditCommand, "AccountID", DbType.Int32, sourceAccount);
db.AddInParameter(creditCommand, "Amount", DbType.Int32, transactionAmount);

// Credit the first account
db.ExecuteNonQuery(creditCommand);
}

private void TestCommand2(Database db, int transactionAmount, int destinationAccount)
{
string sqlCommand = "DebitAccount"
DbCommand debitCommand = db.GetStoredProcCommand(sqlCommand);

db.AddInParameter(debitCommand, "AccountID", DbType.Int32, destinationAccount);
db.AddInParameter(debitCommand, "Amount", DbType.Int32, transactionAmount);

// Debit the second account
db.ExecuteNonQuery(debitCommand);
}

DAAB 在一个事务中可以在一个数据库连接中检测到几个命令的执行，这样可以避免虽然一个数据库连接执行的几个命令而启用分布式事务。在企业类库2.0的DAAB常常启用了分布式事务，就凭这一点，使用企业类库2.0的同学们有必要升级到企业类库3.0。

Parameter Discovery on Ms Access and SqlServer. using Microsoft Patterns and Practices DataBlock version 3.0 final
http://www.codeproject.com/useritems/Parameter_DiscoveryV292.asp

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