Orders.cs

public class GetMyOrdersHandler : IRequestHandler<GetMyOrders, IEnumerable<OrderViewModel>>
{
    private readonly CatalogContext _dbContext;

    public GetMyOrdersHandler(CatalogContext dbContext)
    {
        _dbContext = dbContext;
    }

    public async Task<IEnumerable<OrderViewModel>> Handle(GetMyOrders request,
        CancellationToken cancellationToken)
    {
        var orders = await _dbContext.Orders
            .Include(x => x.OrderItems)
            .Where(x => x.BuyerId == request.UserName)
            .ToArrayAsync(cancellationToken: cancellationToken);

        return orders.Select(o => new OrderViewModel
        {
            OrderDate = o.OrderDate,
            OrderNumber = o.Id,
            ShippingAddress = o.ShipToAddress,
            Total = o.Total()
        });
    }
}