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();

List Controls  00:31:14 
This module shows the Metro controls available to XAML applications for working with collections of items.
This includes the new GridView and ListView controls, 
which are optimized for handling collections in a touch-based user interface. 

Introduction
Items Controls
Demo: ListBox vs ListView
Demo: GridView
Demo: FlipView 
Common ItemsControl
Semantic Zoom
Demo: JumpViewer
Summary