I am developing an application which communicates with an SQL Server 2005 database to execute some stored procedures. My client demands that all transactions be managed on the C# side and not by SQL Server, and so I am using System.Transactions.TransactionScope when accessing the database. However, I have just seen the System.Transactions.Transaction datatype, and I am confused... What are the main pros/cons of each type? Which one should I use?
Please note that I must also use Enterprise Library's Data Access Application Block.
From msdn :
The TransactionScope class provides a
simple way to mark a block of code as
participating in a transaction,
without requiring you to interact with the transaction itself. A
transaction scope can select and
manage the ambient transaction
automatically. Due to its ease of use
and efficiency, it is recommended that
you use the TransactionScope class
when developing a transaction
application. When you instantiate
TransactionScope, the transaction
manager determines which transaction
to participate in. Once determined,
the scope always participates in that
transaction. The decision is based on
two factors: whether an ambient
transaction is present and the value
of the TransactionScopeOption
parameter in the constructor. The
ambient transaction is the transaction
within which your code executes. You
can obtain a reference to the ambient
transaction by calling the static
Current property of the Transaction
class.
You can read more about that here :
http://msdn.microsoft.com/en-us/library/ms172152(v=vs.90).aspx
http://msdn.microsoft.com/en-us/library/system.transactions.transactionscope(v=vs.90).aspx
Great (a bit old) article about transaction in .NET 2.0
http://msdn.microsoft.com/en-us/library/ms973865.aspx
Related
I just want to know if I want to rollback all changes in database if transaction not complete, is there any difference between
using (TransactionScope transaction = new TransactionScope())
and
using (var dbContextTransaction = context.Database.BeginTransaction())
I am confused when read these two:
Connection.BeginTransaction and Entity Framework 4?
and
https://learn.microsoft.com/en-us/ef/ef6/saving/transactions
**note that I use entity framework 4 in my project if its necessary
From Programming Microsoft SQL Server 2012:
There are a number of pain points with explicit transactions. The first difficulty lies in the requirement that every SqlCommand object used to perform updates inside the transaction must have its Transaction property set to the SqlTransaction object returned by BeginTransaction. This means that you must take care to pass along the SqlTransaction object to any place in your code that performs an update, because failing to assign it to the Transaction property of every SqlCommand object in the transaction results in a runtime exception. The issue is compounded when you need to track the SqlTransaction object across multiple method calls that perform updates. It becomes even harder to manage things when these methods need to be flexible enough to work whether or not a transaction is involved or required.
The problem is worse when working with any of the other technologies we'll be covering later that provide abstraction layers over the raw objects. For example, because a SqlDataAdapter actually wraps three distinct SqlCommand objects (for insert, update, and delete), you must dig beneath the data adapter and hook into its three underlying command objects so that you can set their Transaction properties. (We don't generally recommend that you mix and match different data access APIs within your application, but if you must transactionalize updates across a combination of technologies, implicit transactions make it easy.)
The TransactionScope object, introduced as part of a dedicated transaction management API with .NET 2.0 in 2005, lets you code transactions implicitly. This is a superior approach that relieves you from all of the aforementioned burdens associated with explicit transactions. So the guidance here is to always work with implicit transactions whenever possible. You will write less code that is more flexible when you allow the framework to handle transaction management for you. However, it is still also important to understand explicit transactions with the SqlTransaction object, as you might need to integrate with and extend existing code that already uses explicit transactions. Therefore, we will cover both transaction management styles to prepare you for all situations.
The transaction management API offers many more benefits besides implicit transactions. For example, TransactionScope is capable of promoting a lightweight transaction (one associated with a single database) to a distributed transaction automatically, if and when your updates involve changes across multiple databases.
There are two pitfalls with TransactionScope you should be aware of.
First is that it will, by default, create a transaction with SERIALIZABLE isolation level, which, for SQL Server, is a poor choice. So you should always create your TransactionScope like this:
public class TransactionUtils
{
public static TransactionScope CreateTransactionScope()
{
var transactionOptions = new TransactionOptions();
transactionOptions.IsolationLevel = IsolationLevel.ReadCommitted;
transactionOptions.Timeout = TransactionManager.MaximumTimeout;
return new TransactionScope(TransactionScopeOption.Required, transactionOptions);
}
}
See rant here: using new TransactionScope() Considered Harmful
The second is that TransactionScope supports Distributed Transactions. So it will enable you to enlist different connections and even different resource providers in a single transaction. While this is occasionally useful, it's more often a pitfall. If you accidently end up with a distributed transaction you can accidently take a dependency on having a distributed transaction coordinator in your environment. So you should take steps to avoid having a distributed transaction, like shutting down Microsoft Distributed Transaction Coordinator (MSDTC) in your development environment. And ensure that any time you have multiple methods enlisted in a transaction, they don't both have a SqlConnection open at the same time.
While Database. BeginTransaction() is used only for database related operations transaction, System. Transactions. ... TransactionScope for mixing db operations and C# code together in a transaction.
please see Below Links.Hope they help you:
TransactionScope vs Transaction in LINQ to SQL
Database.BeginTransaction vs Transactions.TransactionScope
I've been reading a document from Microsoft's patterns & practices group (Data Access for Highly-Scalable Solutions: Using SQL, NoSQL, and Polyglot Persistence).
In Chapter 3, in the section "Retrieving Data from the SQL Server Database", the authors discuss using Entity Framework to load entities from a database. Here's a bit of their sample code:
using (var context = new PersonContext())
{
Person person = null;
using (var transactionScope = this.GetTransactionScope())
{
person = context.Persons
.Include(p => p.Addresses)
.Include(p => p.CreditCards)
.Include(p => p.EmailAddresses)
.Include(p => p.Password)
.SingleOrDefault(p => p.BusinessEntityId == personId);
transactionScope.Complete();
}
// etc...
}
Note the use of a custom transaction scope via the GetTransactionScope method, implemented in their base context class like so:
public abstract class BaseRepository
{
private static TransactionOptions transactionOptions = new TransactionOptions()
{
IsolationLevel = IsolationLevel.ReadCommitted
};
protected virtual TransactionScope GetTransactionScope()
{
return new TransactionScope(TransactionScopeOption.Required, transactionOptions);
}
}
Working with Transactions (EF6 Onwards) on MSDN states:
In all versions of Entity Framework, whenever you execute SaveChanges() to insert, update or delete on the database the framework will wrap that operation in a transaction [...] the isolation level of the transaction is whatever isolation level the database provider considers its default setting. By default, for instance, on SQL Server this is READ COMMITTED. Entity Framework does not wrap queries in a transaction. This default functionality is suitable for a lot of users
The bold emphasis is mine.
My question: is the use of a TransactionScope as shown above overkill, particularly for data reads, when using Entity Framework?
(I realised after posting that the answer to this question might be somewhat opinion-based, sorry about that.)
The question is a little open ended. But may prove useful for people learning about dirty reads. Isolation and EF.
And you have read EF Transaction Scope ef6 and we have a clear question.
Generally i would say let EF manage the scope.
Beginners dont consider uncommitted reads and it is a good default for EF.
You may have a valid reason to want to control scope.
Or need to use an existing transaction. But remains for specialist use.
So now the real question.
Is it good practice to include such defensive programming around isolation.
My view:
Only if it doesnt make the code harder to maintain, and harder to reuse.
Oracle and SQL server have default Read Committed. I would expect so on other DBs.I would therefore conclude, most likely unecessary protection that adds complexity.
I wouldnt add it to my code.
It depends.
If you want dirty reads, serializable reads,etc anything other than default isolation level, then you need to wrap you queries inside a transaction scope.
To maintain data integrity, it is sometimes useful to use an explicitly defined multi-statement transaction so that if any part of the transaction fails, it all gets rolled back. The decision on whether or not to use a transaction should not be entered into lightly. Explicit transactions, especially distributed ones, come at a major cost to performance and open the system up to deadlocks and to the possibility that a transaction could be left open, locking the affected table and blocking all other transactions. In addition, the code is far more difficult to develop and maintain.
In my experience, I have found that using a transaction scope in C# code is more complicated than using an explicit transaction in SQL. So for operations that would benefit from a transaction, and really any sufficiently complicated query, I would recommend creating a stored procedure to be called from the ORM.
Have you read the following link ?
https://msdn.microsoft.com/en-us/library/vstudio/bb738523%28v=vs.100%29.aspx
If you were to use the normal behavior of saveChanges without it begin part of a transactionscope you would not be able to extend the transaction beyond the boundaries of the database. Using the transaction scope like in the reference above makes the message queue part of the transaction. So if for some reason the sending of the message fails, the transaction fails too.
Of course you might consider this a more complex scenario. In simple applications that don't require such complex logic, you are probably safer to use the plain saveChanges api.
This question already has an answer here:
C# System.Transactions Vs TransactionScope
(1 answer)
Closed 2 years ago.
What is the difference between System.Transactions.TransactionScope and EF6's Database.BeginTransaction?
Could someone give a small example or just explain which one to use when with a clear difference?
P.S: In my project, I'm using EF6. I've already read the documentation but it didn't help much. Also looked up the examples but they are rather using SqlConnection.BeginTransaction and now MS has introduced this new Database.BeginTransaction in EF6.
I found out the answer in Entity Framework 6's documentation:
With the introduction of EF6, Microsoft recommends to use new API methods: Database.BeginTransaction() and Database.UseTransaction(). Although System.Transactions.TransactionScope is still very well supported, it is no longer necessary for most users of EF6.
While Database.BeginTransaction() is used only for database related operations transaction, System.Transactions.TransactionScope, in addition to that, makes it possible for 'plain C# code' to also be transactional.
Hence, use Database.BeginTransaction() where ever doing only db related operations in a transaction in EF6 otherwise use System.Transactions.TransactionScope for mixing db operations and C# code together in a transaction.
For those who still prefer the TransactionScope approach, it is recommended they checkout its limitations, especially in cloud scenarios (cloud scenarios do not support distributed transactions).
Further information can be found here
The accepted and popular answer is misleading.
Both Database.BeginTransaction() and System.Transactions.TransactionScope are for DB operations.
The main differences between Database.BeginTransaction() and System.Transactions.TransactionScope:
Style
With TransactionScope you set the transactions implicitly in the background (by wrapping all transactional actions with a starting using scope = new TransactionScope and an ending scope.Complete(); to commit.
With Database.BeginTransaction the transaction is set explicitly by writing sqlCommand.Transaction = sqlTxn; and context.Database.UseTransaction(sqlTxn);
Distributed Transactions
TransactionScope supports both distributed transactions (where multiple DB involved in a single transaction) and non-distributed transactions.
Database.BeginTransaction only supports non-distributed transactions (a local transaction where all actions are done within a single DB).
MSDN do state that with the new Database.BeginTransaction() and Database.UseTransaction() APIs, the TransactionScope approach is no longer necessary for most users.
Async Support
For async support the TransactionScope should be passed the AsyncFlow enabled flag - TransactionScope(TransactionScopeAsyncFlowOption.Enabled); in case await is used after opening the transaction (e.g. await _myReop.SaveItemAsync(item);).
Advantages and disadvantages of TransactionScope:
Disadvantages of TransactionScope:
Requires .NET 4.5.1 or greater to work with asynchronous methods.
It cannot be used in cloud scenarios unless you are sure you have one and only one connection (cloud scenarios do not support distributed transactions).
It cannot be combined with the Database.UseTransaction() approach of the previous sections.
It will throw exceptions if you issue any DDL and have not enabled distributed transactions through the MSDTC Service.
Advantages of TransactionScope:
It will automatically upgrade a local transaction to a distributed transaction if you make more than one connection to a given database or combine a connection to one database with a connection to a different database within the same transaction (note: you must have the MSDTC service configured to allow distributed transactions for this to work).
Ease of coding. If you prefer the transaction to be ambient and dealt with implicitly in the background rather than explicitly under you control then the TransactionScope approach may suit you better.
Based on this MSDN article.
I have a piece of code i recently expanded but now must use a transaction. It looks like it can only be access while in a transaction but looks like doesnt make me feel comfortable. Using SQLite and ADO.NET i wrote if(cmd.Transaction==null) but it is null and in a transaction. How should i check?
NOTE: I will be using this code with TSQL in the future. This is a quick prototype with SQLite
-edit- i was thinking of nesting transactions but this code generates a piece of sql and uses a command to add parameters too. So adding a nested transaction would take a lot of modification.
Depending on the nature of the SQL and its fit in the application, it may be more appropriate for you to nest transactions, ensuring a transaction is present regardless of the context of the call.
For example, you could wrap the calling code in a TransactionScope block. If there is a transaction present, this will have no real effect on the operation. If there is no transaction present, it will create a transaction and ensure the ADO.NET code participates in the transaction.
This approach only works if you're happy for the SQL to be executed as a single operation. If it should only be called as part of a larger transaction, this approach doesn't help.
To know for sure that a transaction is present, you have to check for the explicit transaction on the ADO.NET command (as you have above) and also the presence of an ambient transaction from the System.Transactions programming model using the Transaction.Current property.
I am using WF, and need to support transactions and persistence.
I would like not to use the TransactionScopeActvity , but use my own transaction scope object, and still have a persistence point at the end which will be part of the transaction in the activity itself (similar to how the TransactionScopeActvity works on this aspect). I can achieve a persistence point at the end of the transaction by using the "PersistOnClose" attribute, but to what transaction will the persistence call belong to? will it open a new transaction, or look for the ambient transaction? How can I assure that an ambient transaction exists when the persistence point is activated?
Version 3 and 3.5 does not support ambient transaction I faced a lot of Issues designing around this In the new version of workflow i.e. 4.0 (which is complete rewrite from ground up ) supports Ambient Transaction