I am getting these errors now since I upgraded to 4.1. They happen even more when i am debugging the site in visual studio.
System.InvalidOperationException: A second operation started on this context before a previous operation completed. Any instance members are not guaranteed to be thread safe.
at Microsoft.EntityFrameworkCore.Internal.ConcurrencyDetector.EnterCriticalSection()
at Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext()
at System.Collections.Generic.List`1.AddEnumerable(IEnumerable`1 enumerable)
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at Nop.Services.Catalog.ReviewTypeService.<>c__DisplayClass10_0.<GetProductReviewReviewTypeMappingsByProductReviewId>b__0() in C:\Projects\Main\NopCommerce\lifeseasons.com.4.1\Libraries\Nop.Services\Catalog\ReviewTypeService.cs:line 135
at Nop.Core.Caching.MemoryCacheManager.Get[T](String key, Func`1 acquire, Nullable`1 cacheTime) in C:\Projects\Main\NopCommerce\lifeseasons.com.4.1\Libraries\Nop.Core\Caching\MemoryCacheManager.cs:line 152
at Nop.Services.Catalog.ReviewTypeService.GetProductReviewReviewTypeMappingsByProductReviewId(Int32 productReviewId) in C:\Projects\Main\NopCommerce\lifeseasons.com.4.1\Libraries\Nop.Services\Catalog\ReviewTypeService.cs:line 133
at Nop.Web.Factories.ProductModelFactory.PrepareProductReviewsModel(ProductReviewsModel model, Product product) in C:\Projects\Main\NopCommerce\lifeseasons.com.4.1\Presentation\Nop.Web\Factories\ProductModelFactory.cs:line 1440