private static void LazyLoading()
{
using (var context = new FroshDbContext(ConnectionString))
{
// Voraussetzungen für Lazy Loading
context.Configuration.LazyLoadingEnabled = true; // Default
// Alle Navigationsproperties virtual!
var customers = context.Customers.OrderBy(c => c.Lastname)
.ThenBy(c => c.Firstname)
.Take(20).ToList();
//var customer = context.Customers.First();
// N+1 Problem
foreach (var customer in customers)
{
Console.WriteLine($"{customer.Firstname} {customer.Lastname}");
foreach (var p in customer.Products)
{
Console.WriteLine($"\t{p.Name}");
}
}
}
}
private static void GenerateSampleData()
{
var customerFiller = new Filler <Customer>();
customerFiller.Setup()
.OnProperty(c => c.Id).IgnoreIt()
.OnProperty(c => c.Products).IgnoreIt()
.OnProperty(c => c.Firstname).Use(new RealNames(NameStyle.FirstName))
.OnProperty(c => c.Lastname).Use(new RealNames(NameStyle.LastName));
var productfiller = new Filler <Product>();
productfiller.Setup()
.OnProperty(p => p.Id).IgnoreIt()
.OnProperty(p => p.Customers).IgnoreIt()
.OnProperty(p => p.Number).Use(new PatternGenerator("P-{A:8}"))
.OnProperty(p => p.Name).Use(new RandomListItem <string>(
"Apfel", "Birne", "Banane", "Mango", "Kiwi", "Kirsche",
"Drachenfrucht", "Banane", "Kokusnuss", "Litschi", "Papaya",
"Clementine", "Grapefruit", "Himbeere", "Honigmelone"))
.OnProperty(p => p.Description).Use(new Lipsum(LipsumFlavor.InDerFremde));
var customers = customerFiller.Create(200);
var products = productfiller.Create(500).ToList();
var random = new Random();
foreach (var c in customers)
{
for (int i = 0; i < random.Next(3, 50); i++)
{
var randomProductIndex = random.Next(0, products.Count);
c.Products.Add(products[randomProductIndex]);
}
}
using (var context = new FroshDbContext(ConnectionString))
{
context.Customers.AddRange(customers);
context.SaveChanges();
}
}
private static void EagerLoading()
{
using (var context = new FroshDbContext(ConnectionString))
{
// wichtig: using System.Data.Entity;
var customers = context.Customers.Include(c => c.Products)
.OrderBy(c => c.Lastname)
.ThenBy(c => c.Firstname)
.Take(20)
.ToList();
foreach (var customer in customers)
{
Console.WriteLine($"{customer.Firstname} {customer.Lastname}");
foreach (var p in customer.Products)
{
Console.WriteLine($"\t{p.Name}");
}
}
}
}
private static void ChangeTracker()
{
using (var context = new FroshDbContext(ConnectionString))
{
var customers = context.Customers.AsNoTracking().OrderBy(c => c.Lastname)
.ThenBy(c => c.Firstname)
.Take(20)
.ToList();
var customer = customers.First();
customer.Firstname = "whatever";
context.Customers.Attach(customer);
//context.Entry(customer).State = EntityState.Modified;
context.Entry(customer).Property(c => c.Firstname).IsModified = true;
foreach (var entry in context.ChangeTracker.Entries())
{
Console.WriteLine(entry.State);
}
}
}