Multiple connections in one transaction, on Azure - entity-framework

Question

We are building an application, that is using a legacy framework utilising ADO.NET. This framework manages its own connection to the DB for calls to its code API.
For any customisations and custom tables we are using Entity Framework and hence a separate connection to the DB is made.
The application and DB is to be hosted on Azure.
What we would like to do is wrap both calls to the legacy framework and to Entity Framework into the same transaction.
Our understanding is that this is a distributed transaction, but this feature is not available in Azure.
Is there a way to make this to work in the Azure environment?
e.g.
using (var transaction = new TransactionScope())
{
using (var db = new EntityFrameworkDBEntities())
{
Order order = db.Orders.FirstOrDefault();
order.Name = "1";
db.SaveChanges();
}
using (var legacyAPI = new LegacyAPI())
{
Customer customer = legacyAPI.GetCustomers.FirstOrDefault();
customer.Name = "Charles";
legacyAPI.SaveCustomer(customer);
}
transaction.Complete();
}

Answer 1

AFAIK you need to use the same connection for your transaction since SQL Azure doesn't support distributed transaction. ADO.NET will upgrade to distributed transaction if you utilizes multiple connections in the same transaction even though all of them are connected to the same database.

Answer 2

As Shaun Xu says, you need to use just one connection. If you are able to change your LegacyAPI to take an open connection and a transaction as input, here is how, using EF6 and edmx:
var workspace = new MetadataWorkspace(new[] { "res://*/" }, new[] { Assembly.GetExecutingAssembly() });
using (var connection = new SqlConnection("Normal ADO connection string with MultipleActiveResultSets=True"))
{
using (var entityConnection = new EntityConnection(workspace, connection, false))
{
connection.Open();
using (var transaction = connection.BeginTransaction())
{
using (var db = new EntityFrameworkDBEntities(entityConnection))
{
db.Database.UseTransaction(transaction);
// Do stuff with db
db.SaveChanges();
}
// Do ADO stuff on LegacyAPI using the connection and transaction objects
transaction.Commit();
}
}
}
To obtain the extra constructor on your dbcontext, you make this partial class, where false indicates that you open and close the connection manually.
partial class EntityFrameworkDBEntities
{
public EntityFrameworkDBEntities(DbConnection connection) : base(connection, false) { }
}
As a bonus you now only need one connection string in your config and it doesn't include all the useless EF junk that normally comes with it (metadata=res://*/blabla).
This also works if, say, you have a database with multiple schemas and an edmx for each. Note that although the EntityConnections are identical, you need one for each dbcontext.