TransactionScope和Enterprise Libray 3.0 Data Access Application Block

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
[url]http://www.codeproject.com/useritems/Parameter_DiscoveryV292.asp[/url]

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