Transactions in 'NET

1
Transactions in .NET
2
Agenda

• Overview
• Transactions in T-SQL
• Transactions in ADO.NET
• Transactions in COM

3
What is a Transaction?

• A transaction is a set of related tasks that
  either succeed or fail as a unit.

4
ACID

• Atomicity
• A transaction must be an atomic unit of work
  either all of its data modifications are
  performed, or none of them is performed.
• Consistency
• When completed, a transaction must leave all data
  in a consistent state.
• Isolation
• Modifications made by concurrent transactions
  must be isolated from the modifications made by
  other concurrent transactions.
• Durability
• After a transaction has completed, its effects
  are permanently in place in the system.

5
Transaction Log

• The transaction log records the start of each
  transaction. It records the changes to the data
  and enough information to undo the modifications
  (if necessary later) made during each transaction

6
.NET Transactions

• Automatic
• Manual

7
Manual Transactions

• SqlTransaction Class
• SqlConnection.BeginTransaction()
• conn.Open()
• SqlTransaction trans conn.BeginTransaction()

8
Manual Transactions

• trans.Commit()
• trans.Rollback()
• trans.IsolationLevel
• try
• //Execute db stuff here
• //Note that trans must be set for each command
• trans.Commit()
• catch
• trans.Rollback()

9
Automatic Transactions

• Pages and Web Services can simply be marked as
  requiring transactions.
• Classes inherit from ServicedComponent and
  interact with COM more directly

10
Automatic Transactions - Page

• lt_at_ Page Transaction"Required" gt
• Disabled
• Not Supported
• Supported
• Required
• RequiresNew

11
Automatic Transactions - Webmethods

• WebMethod(TransactionOptionTransactionOption.Re
  quiresNew)
• public void MyWebMethod()

12
Automatic Transactions

• Examples

13
Automatic Transactions - Class

• Apply the TransactionAttribute to your class.
• Derive your class from the ServicedComponent
  Class.
• Sign the assembly with a strong name.
• Add the AssemblyKeyFileAttribute or
  AssemblyKeyNameAttribute assembly attribute
• Register the assembly that contains your class
  with the COM catalog.

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Automatic Transactions - Class

• //COM application name in the COM catalog.
• assembly ApplicationName("TestApp")
• //Strong name for assembly.
• assembly AssemblyKeyFileAttribute("TestApp.snk")
  
• //Transaction Requirements
• Transaction(TransactionOption.Required)
• public class Account ServicedComponent

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Automatic Transactions Class

• Transaction(TransactionOption.Supported)
• public class Account ServicedComponent
• AutoComplete
• public void Debit(int amount)
• // Do some database work.
• // Any exception thrown here aborts the
  transaction
• // otherwise, transaction commits.
• You can also use ContextUtil.SetAbort() and
  ContextUtil.SetComplete() to vote on completion
  of the transaction (in distributed transactions)

16
Discussion

• How to best transact object models?

17
Summary

• Transactions and ACID Good Trip
• No Transactions Bad Trip

18
Where to Get More Information

• SQL Books Online
• VS.NET Docs
• Professional ADO.NET