DbContext per request aspboilerplate

问题

I need to implement multithreading background job for import file. I have implemented it with background job(Hangfire). But if i use one thread it goes very slow. The function look like this.

I using non-transaction unit to save changes to db immediately.

var contactFound = await _contactRepository.FirstOrDefaultAsync(x => x.Email.ToLower() == contact.Email.ToLower());

            if (contactFound != null)
            {
                await _bjInfoManager.AddLog(args.JobId, "Found duplicated email: " + contact.Email);

            }
            else
            {
                contact.ContactListId = args.ContactListId;
                contact.Email = contact.Email.ToLower();

                await _contactRepository.InsertAsync(contact);

                //Save changes in db
                await CurrentUnitOfWork.SaveChangesAsync();
            }

The problem occur when I tries to use this with Producer-Consumer Dataflow Pattern. I throws the exception "A second operation started on this context before a previous asynchronous operation completed."

The question is how to create isolated DbContext inside this method. Please help me.

回答1:

Transactions should not be multi-threaded. If you create a new task/thread in a UOW, you can create a seperated UOW using IUnitOfWork.Begin(TransactionScopeOption.RequiresNew) in a using block.

See the links

https://github.com/aspnetboilerplate/aspnetboilerplate/issues/619
Does Entity Framework support Multi-Threading?
Entity Framework and Multi threading

If you are using Microsoft SQL Server, then I recommend you to use bulk insert. It's super fast than entity framework.

https://docs.microsoft.com/en-us/sql/t-sql/statements/bulk-insert-transact-sql

来源：https://stackoverflow.com/questions/47710541/dbcontext-per-request-aspboilerplate

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