在foreach .net 4.5 mvc中实现异步

Question

in working to develop a new post method. I found that I am running into extremely long wait times on a bottleneck foreach statement. I am saving between 5 and 8k(depending on the items being sent) to the database. The method succeeds, but usually takes upwards of a full 60 seconds. I have been looking into how to actually execute an async method, but I am not sure this will actually solve the problem.

This is the full method

[HttpPost]
        public ActionResult ConfirmSend(int? SystemGeneralAnnouncementId) { 
        var systemGeneralAnnouncement = (SystemGeneralAnnouncementId == null) ? null : _uow.SystemGeneralAnnouncementRepository.GetById(SystemGeneralAnnouncementId.Value);
        List<Status> status = new List<Status>();

            if (systemGeneralAnnouncement.Statuses.Length > 0)
            {
                status.AddRange(systemGeneralAnnouncement.Statuses.Split(',').Select(item => (Status) Enum.Parse(typeof (Status), item)));
            }

            var allEmailAddresses = new List<PointOfContact>();
            var EmailAddresses = new List<PointOfContact>();


            var result = new List<PointOfContact>();
            foreach (var item in status)
            {
                result = _uow.PointOfContactRepository.GetAllByStatus(item).ToList();
                allEmailAddresses.AddRange(result);
            }


            if (systemGeneralAnnouncement.SendToRecipients.Contains("(1) All Three Contact Types"))
            {
                mailAddresses = allEmailAddresses;
            }
            else
            {
                if (systemGeneralAnnouncement.SendToRecipients.Contains("(2) All Contacts "))
                {
                    EmailAddresses.AddRange(allEmailAddresses.Where(r => r.PointOfContactType == PointOfContactTypes.Primary).ToList());
                }
                if (systemGeneralAnnouncement.SendToRecipients.Contains("(3) All Compliance contacts"))
                {
                    pocEmailAddresses.AddRange(allEmailAddresses.Where(r => r.PointOfContactType == PointOfContactTypes.Secondary).ToList());
                }
                if (systemGeneralAnnouncement.SendToRecipients.Contains("(4) All Authorities"))
                {
                    pocEmailAddresses.AddRange(allEmailAddresses.Where(r => r.PointOfContactType == PointOfContactTypes.SigningAuthority).ToList());
                }
                if (systemGeneralAnnouncement.SendToRecipients.Contains("(5) All Rate Contacts"))
                {
                    EmailAddresses.AddRange(allEmailAddresses.Where(r => r.PointOfContactType == PointOfContactTypes.TuitionRates).ToList());
                }
                if (systemGeneralAnnouncement.SendToRecipients.Contains("(6) Specified Email Address"))
                {
                    var pocs = new List<PointOfContact>();

                    string[] emails = systemGeneralAnnouncement.EmailAddresses.Split(',');

                    foreach (string email in emails)
                    {                      
                        var addContact = new InstitutionPointOfContact { Email = email };

                        User user = _uow.UserRepository.GetByEmail(email);

                        if (user == null)
                        {
                            addContact.FirstName = "Not Created Account Yet";
                        }
                        else
                        {
                            addContact.FirstName = user.FirstName;
                            addContact.LastName = user.LastName;
                        }

                        List<PointOfContact> idAssociatedToUser =
                            _uow.PointOfContactRepository
                                .GetAllByEmail(email)
                                .ToList();


                        if (idAssociatedToUser.Count == 0)
                        {
                            addContact.IDNumber = "N/A";
                        }
                        else
                        {
                            string[] opeidArray = opeidAssociatedToUser
                                .Select(x => x.OPEIDNumber)
                                .ToArray();

                            addContact.OPEIDNumber = string.Join(",", opeidArray);
                        }
                        Contacts.Add(addContact);
                    }                  
                    EmailAddresses.AddRange(Contacts);
                }
            }

The Specific Foreach

    if (EmailAddresses.Count > 0)
                {
                    foreach (PointOfContact emailAddress in EmailAddresses.Where(x => x.Email != "").ToList())
                    {
                        string firstName = emailAddress.FirstName == null ? "" : emailAddress.FirstName.Trim();
                        string lastName = emailAddress.LastName == null ? "" : emailAddress.LastName.Trim();

                        string userName = firstName + " " + lastName;

                        string emailBody = WebUtility.HtmlDecode(systemGeneralAnnouncement.EmailBody);

                        SaveToDatabase(emailAddress.Email, emailBody, systemGeneralAnnouncement.Subject, UserIdentityHelper.GetUserEmailAddress + " (" + UserIdentityHelper.GetUserId + ")", systemGeneralAnnouncement.SystemGeneralAnnouncementId, userName, emailAddress.OPEIDNumber);
                        LogInstitutionEmail(systemGeneralAnnouncement.Subject, emailBody, emailAddress.Email, emailAddress.OPEIDNumber, systemGeneralAnnouncement.EmailAttachmentLocation);
                    }
                }
                return View("GeneralAnnouncementGeneratedConfirmation");
            }

And the Database methods:

        private void LogInstitutionEmail(string subject, string emailBody, string email, string opeidNumber, string emailAttachment)
        {
            try
            {
                using (var conn = new SqlConnection(ConfigurationManager.ConnectionStrings["MasterContext"].ConnectionString))
                {
                    conn.Open();
                    var cmd = new SqlCommand("Insert Into InstitutionEmails (Since, Subject, Email, EmailAddress, OpeidNumber, FirstReadDateTime, Attachment) VALUES(@Since, @Subject, @Email, @EmailAddress, @idNumber, NULL, @Attachment)", conn);
                    cmd.CommandType = CommandType.Text;
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@Since", Value = DateTime.Now });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@Subject", Value = subject });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@Email", Value = emailBody });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@EmailAddress", Value = email });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@idNumber", Value = idNumber });

                    if (!string.IsNullOrEmpty(emailAttachment))
                    {
                        cmd.Parameters.Add(new SqlParameter() { ParameterName = "@Attachment", Value = emailAttachment });
                    }

                    cmd.ExecuteNonQuery();
                    conn.Close();
                }
            }
            catch (Exception ex)
            {
            }
        }

        private void SaveToDatabase(string emailRecipient, string emailBody, string subject, string userWhoSentIt, int systemGeneralAnnouncementId, string userName, string opeidNumber)
        {
            try
            {
                using (var conn = new SqlConnection(ConfigurationManager.ConnectionStrings["MasterContext"].ConnectionString))
                {
                    conn.Open();
                    var cmd = new SqlCommand("Insert Into EmailQueue (EmailRecipients, EmailBody, EmailSubject, UserWhoSentIt, QueueDate, SystemGeneralAnnouncementId, UserName, idNumber) VALUES(@EmailRecipients, @EmailBody, @EmailSubject, @UserWhoSentIt, @QueueDate, @SystemGeneralAnnouncementId, @UserName, @idNumber)", conn);
                    cmd.CommandType = CommandType.Text;
                    cmd.Parameters.Add(new SqlParameter() {ParameterName = "@EmailRecipients", Value = emailRecipient });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@EmailBody", Value = emailBody });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@EmailSubject", Value = subject });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@UserWhoSentIt", Value = userWhoSentIt });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@QueueDate", Value = DateTime.Now });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@SystemGeneralAnnouncementId", Value = systemGeneralAnnouncementId });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@UserName", Value = userName });
                    cmd.Parameters.Add(new SqlParameter() { ParameterName = "@idNumber", Value = idNumber });


                    cmd.ExecuteNonQuery();
                    conn.Close();
                }
            }
            catch (Exception ex)
            {
            }
        }

My Question is two fold. First, is async a viable option with this type of Code (Using Sql server 2012) as I noticed in my research that if you have a database level bottleneck, async could potentially cause dead lock. Second, If Async/await is viable, what would be the best way to actually implement it?

Update : The post method is only retrieving the Id of the SystemGeneralAnnouncement, and the confirmation to start the method. All of the actual execution is being handled inside the method itself.

Update 2: For clarifications Sake, these items are being passed to a task scheduler that fires at a later date, and takes all the stored items in the queue, then delivers them in the background. This is why I am using the SQL call.

Answer 1

if you have a database level bottleneck, async could potentially cause dead lock

Not at all.

However, async won't help you run faster - that's a common misconception.

What you want to do is a batch update.