In summary, the most important issues here are:
- The Aggregate’s main task is to protect invariants (business rules, the boundary of immediate consistency)
- In a multi-threaded environment, when multiple threads are running simultaneously on the same Aggregate, a business rule may be broken
- A way to solve concurrency conflicts is to use Pessimistic or Optimistic concurrency techniques
- Pessimistic Concurrency involves the use of a database transaction and a locking mechanism. In this way, requests are processed one after the other, so basically concurrency is lost and it can lead to deadlocks.
- Optimistic Concurrency technique is based on versioning database records and checking whether the previously loaded version has not been changed by another thread.
- Entity Framework Core supports Optimistic Concurrency. Pessimistic Concurrency is not supported
- The Aggregate must always be treated and versioned as a single unit
- Domain events are an indicator, that state was changed so Aggregate version should be changed as well
public class AggregateRootBase : Entity, IAggregateRoot { private int _versionId; public void IncreaseVersion() { _versionId++; } }
internal sealed class OrderEntityTypeConfiguration : IEntityTypeConfiguration<Order> { public void Configure(EntityTypeBuilder<Order> builder) { builder.Property("_versionId").HasColumnName("VersionId").IsConcurrencyToken(); //... } }
var order = await _ordersContext.Orders.FindAsync(orderId); order.AddOrderLine(request.ProductCode); var domainEvents = DomainEventsHelper.GetAllDomainEvents(order); if (domainEvents.Any()) { order.IncreaseVersion(); } await _ordersContext.SaveChangesAsync();
- An error occurred while generating the SSH keys. Please check that the environment is properly configured. Details: cat: /Users/cc/Library/Caches/Xamarin/XMA/Keys/1984b83a-dde9-4031-919d-b1d1b8411d0d: No such file or directory
- InvalidOperationException while debugging Xamarin Forms app
- Frame note in module in Xamarin Forms Android
- Internal compiler error is fixed and analysis for WDK completes as usual.
- We fixed an issue in the new Find in Files experience where hidden files and auto-generated files were not searchable.
- Fixed issue with deployment of UWP apps to remote machines where deployment fails with message "DEP0600: Deployment failed. DkmException - Error in the application."
- Local static variable not initialized in inlined function of class imported from dll
- VS 2019 16.5.X: Multiple startup projects while Live Visual Tree was last opened in a debug session crashes
- Fixed issues where for the C++ formatting indentation of new lines with only ending parenthesis.
- Fixed a bug preventing some users from installing 16.5
- Fix an issue where Visual Studio can crash when the display configuration changes.
- Fixed an issue causing slow downs when opening solutions that are impacting the IntelliSense code and related operations.
- Fixed a crash with the debugger that users can run into when the target application being debugged raises an exception.
- Added support for Xcode 11.4.
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