How to create an aspect decorator to handle EF transactions

Question

I'm working (maintaining) on a dll assembly that acts as a Data Access Layer, there are many methods that requires transaction handling, many other do not, it's a currently "functional" dll, without any transaction handling method, I need to add it, so I'm looking for an easy way to add a transaction handler.

I'm wondering if is it possible to use AOP to create a decorator that I can add to the methods that requires a transaction.

I would like to have something like this:

[Transaction]
void MyDbMethod()
{
  //DoSomething
  myContext.SaveChanges();  
}

For the EF model definition I'm using Code First, the current project uses Unity framework for some other DI tasks, can that framework be used for this?

Answer 1

If someone faces this same issue, I did not found any "by hand" solution, instead I used the PostSharp library and its OnMethodBoundaryAspect class, but be careful, at this moment the free/express license has limitations about the amount of classes where you can use it, so read carefully its limitations.

using System.Transactions;
using PostSharp.Aspects;
using PostSharp.Serialization;

namespace MyProject
{
    [PSerializable]
    public class Transaction : OnMethodBoundaryAspect
    {
        public Transaction()
        {
            //Required if the decorated method is async
            ApplyToStateMachine = true;
        }

        public override void OnEntry(MethodExecutionArgs args)
        {
            //TransactionScopeAsyncFlowOption.Enabled => Required if the decorated method is async
            var transactionScope = new TransactionScope(TransactionScopeOption.Required, TransactionScopeAsyncFlowOption.Enabled);
            args.MethodExecutionTag = transactionScope;
        }

        public override void OnSuccess(MethodExecutionArgs args)
        {
            var transactionScope = (TransactionScope)args.MethodExecutionTag;
            transactionScope.Complete();
        }

        public override void OnExit(MethodExecutionArgs args)
        {
            var transactionScope = (TransactionScope)args.MethodExecutionTag;
            transactionScope.Dispose();
        }
    }
}