Async / Await in Foreach Loop (ovvero cicli di modelli ef) Genera un errore

Ho un ciclo foreach e la prima volta che gira nel primo elemento funziona, ma quando arriva al prossimo elemento, ottengo questo errore.

System.InvalidOperationException
  HResult=0x80131509
  Message=Error generated for warning 'Microsoft.EntityFrameworkCore.Infrastructure.LazyLoadOnDisposedContextWarning: An attempt was made to lazy-load navigation property 'Company' on entity type 'RecurringInvoiceTemplateProxy' after the associated DbContext was disposed.'. This exception can be suppressed or logged by passing event ID 'CoreEventId.LazyLoadOnDisposedContextWarning' to the 'ConfigureWarnings' method in 'DbContext.OnConfiguring' or 'AddDbContext'.
  Source=Microsoft.EntityFrameworkCore
  StackTrace:
   at Microsoft.EntityFrameworkCore.Diagnostics.EventDefinition`2.Log[TLoggerCategory](IDiagnosticsLogger`1 logger, WarningBehavior warningBehavior, TParam1 arg1, TParam2 arg2, Exception exception)
   at Microsoft.EntityFrameworkCore.Internal.CoreLoggerExtensions.LazyLoadOnDisposedContextWarning(IDiagnosticsLogger`1 diagnostics, DbContext context, Object entityType, String navigationName)
   at Microsoft.EntityFrameworkCore.Internal.LazyLoader.ShouldLoad(Object entity, String navigationName, NavigationEntry& navigationEntry)
   at Microsoft.EntityFrameworkCore.Internal.LazyLoader.Load(Object entity, String navigationName)
   at Microsoft.EntityFrameworkCore.Proxies.Internal.LazyLoadingInterceptor.Intercept(IInvocation invocation)
   at Castle.DynamicProxy.AbstractInvocation.Proceed()
   at Castle.Proxies.RecurringInvoiceTemplateProxy.get_Company()
   at SourceLine.Api.Services.InvoicingService.<>c__DisplayClass48_0.<GenerateRecurringInvoicesAsync>b__0(CustomerDto x) in 1299
   at System.Linq.Enumerable.TryGetFirst[TSource](IEnumerable`1 source, Func`2 predicate, Boolean& found)
   at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at SourceLine.Api.Services.InvoicingService.<GenerateRecurringInvoicesAsync>d__48.MoveNext() in line 1299
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()

la mia domanda

 return dbContext.RecurringInvoiceTemplates.Include(x => x.Company)
                                              .Include(x => x.RecurringInvoiceFrequency)
                                              .Where(x => x.NextRun.Date.CompareTo(currentTime.Date) <= 0).ToList();

Interrogarsi muore

    foreach (var r in recurringInvoices){
     var foundCustomer = allCustomers.FirstOrDefault(x => x.Id == r.Company.Identifier);
}

Aggiornare

Il problema potrebbe essere in realtà è a causa di questo

public async void Get(){

    var recurringInvoices = dbContext.RecurringInvoiceTemplates.Include(x => x.Company)
                                                  .Include(x => x.RecurringInvoiceFrequency)
                                                  .Where(x => 
    var allCustomer = new List<Dto>(){
        new Dto(){
            Id = 1
        }
    }

    foreach (var r in recurringInvoices)
    {
        //allcustomers is not en EF object, just a dto.
        var foundCustomer = allCustomers.FirstOrDefault(x => x.Id == r.Company.Identifier);

        if (foundCustomer != null)
        {

                var ApiKey = configuration["SendGrid:Key"];
                var sendGridClient = new SendGridClient(ApiKey);

                var msg = new SendGridMessage();
                msg.SetFrom(new EmailAddress("example@test.com, "Example User"));


                msg.SetTemplateId("d-f06bfad7374b4a3cb2ccbf846d8e96a4");


                var dynamicTemplateData = new SendInvoiceTemplateDto
                {
                    Subject = "a",
                    Body = "b"
                };

                msg.SetTemplateData(dynamicTemplateData);

                var response = await sendGridClient.SendEmailAsync(msg);
            }
        }
}

Quindi sembra che dal momento che sto usando async disponga il mio dbContext?

Modifica 2

Non capisco ma quando lo uso

 var response = sendGridClient.SendEmailAsync(msg);
response.Wait();

Non ho più questo problema.