private static void PerformanceCount()
{
var totalCount = 0l;
var totalToListCount = 0l;
var iterations = 100.0;
for (int i = 0; i < iterations; i++)
{
using (var context = new LostStarsDbContext())
{
context.Galaxies.First();
using (new Stopwatch(ms => totalCount += ms))
context.Stars.Count();
using (new Stopwatch(ms => totalToListCount += ms))
context.Stars.ToList().Count();
}
Console.WriteLine($"{i}/{iterations}");
}
using (var context = new LostStarsDbContext())
{
var countStars = context.Stars.Count();
Console.WriteLine($"{countStars} Stars");
}
Console.WriteLine($"{iterations} * Count() took {totalCount}ms");
Console.WriteLine($" - average {(totalCount / iterations):0.00}ms");
Console.WriteLine($"{iterations} * ToList().Count() took {totalToListCount}ms");
Console.WriteLine($" - average {(totalToListCount / iterations):0.00}ms");
// !!! NEVER use ToList().Count or ToList().Count() just to count !!!
}
private static void Concurrency()
{
using (var firstContext = new LostStarsDbContext())
using (var secondContext = new LostStarsDbContext())
{
var firstGalaxyFromFirstContext = firstContext.Galaxies.First();
var firstGalaxyFromSecondContext = secondContext.Galaxies.First();
Console.WriteLine($"Galaxy from FirstContext: {firstGalaxyFromFirstContext.Name}");
Console.WriteLine($"Galaxy from SecondContext: {firstGalaxyFromSecondContext.Name}");
Console.WriteLine($"Are the same Object: {Equals(firstGalaxyFromFirstContext, firstGalaxyFromSecondContext)}");
var aGalaxyNameHopefullyNobodyProvides = "0fe5VsvHkib7sWcL46Pc5KqIHjASTce8M6VIpucXEObtAQTmsGQBhSKxp2j8llDs5wT378XVzc9AxRDf";
firstGalaxyFromFirstContext.Name = aGalaxyNameHopefullyNobodyProvides;
Save(firstContext);
Console.Write("How do you want to rename the galaxy? ");
var newGalaxyName = Console.ReadLine();
while (string.IsNullOrWhiteSpace(newGalaxyName))
{
Console.WriteLine("Please provide a galaxy name!");
newGalaxyName = Console.ReadLine();
}
firstGalaxyFromSecondContext.Name = newGalaxyName;
Save(secondContext);
}
}
private static void PerformanceAsNoTracking()
{
var totalWithTracking = 0l;
var totalAsNoTracking = 0l;
const int iterations = 100;
for (int i = 0; i < iterations; i++)
{
using (var context = new LostStarsDbContext())
{
context.Galaxies.First();
using (new Stopwatch(t => totalWithTracking += t))
context.Stars.ToList();
}
using (var context = new LostStarsDbContext())
{
context.Galaxies.First();
using (new Stopwatch(t => totalAsNoTracking += t))
context.Stars.AsNoTracking().ToList();
}
Console.WriteLine($"{i + 1}/{iterations}");
}
using (var context = new LostStarsDbContext())
{
var countStars = context.Stars.Count();
Console.WriteLine($"{countStars} Stars");
}
Console.WriteLine($"{iterations} * WithTracking took {totalWithTracking}ms");
Console.WriteLine($" - average {(totalWithTracking / (double)iterations):0.00}ms");
Console.WriteLine($"{iterations} * AsNoTracking took {totalAsNoTracking}ms");
Console.WriteLine($" - average {(totalAsNoTracking / (double)iterations):0.00}ms");
}
private static void Save(LostStarsDbContext context)
{
try
{
context.SaveChanges();
}
catch (System.Data.Entity.Infrastructure.DbUpdateConcurrencyException ex)
{
foreach (var entry in ex.Entries)
{
var dbValues = entry.GetDatabaseValues();
var modifiedNames = entry.CurrentValues.PropertyNames.Where(n => entry.Property(n).IsModified);
Console.WriteLine($"\nA {entry.Entity.GetType().Name} was edited in the Database.");
foreach (var modifiedName in modifiedNames.Where(n => n.ToLower() != "timestamp"))
{
Console.WriteLine($"Original Value for Property {modifiedName}: {entry.OriginalValues.GetValue<object>(modifiedName)}");
Console.WriteLine($"Your Value for Property {modifiedName}: {entry.CurrentValues.GetValue<object>(modifiedName)}");
Console.WriteLine($"Database Value for Property {modifiedName}: {dbValues.GetValue<object>(modifiedName)}");
}
var wasInputInvalid = true;
while (wasInputInvalid)
{
wasInputInvalid = false;
Console.WriteLine("\nWhich Values would you like to keep?");
Console.WriteLine(" (1) Original Values");
Console.WriteLine(" (2) Your Values");
Console.WriteLine(" (3) Database Values");
var input = Console.ReadLine();
switch (input)
{
case "1":
entry.CurrentValues.SetValues(entry.OriginalValues);
entry.OriginalValues.SetValues(dbValues);
break;
case "2":
entry.OriginalValues.SetValues(dbValues);
break;
case "3":
entry.Reload();
break;
default:
Console.WriteLine("Invalid Input");
wasInputInvalid = true;
break;
}
}
}
Save(context);
}
}
private static async void CreateSampleData()
{
// http://objectfiller.net/
// https://objectfillernet.readme.io/v1.5.3/reference
var galaxyFiller = new Filler <Galaxy>();
galaxyFiller.Setup()
.OnProperty(g => g.Id).IgnoreIt()
.OnProperty(g => g.Stars).IgnoreIt()
.OnProperty(g => g.Name).Use(new RealNames(NameStyle.FirstName))
.OnProperty(g => g.DiscoveryDate).Use(new DateTimeRange(DateTime.Now.AddYears(-300), DateTime.Now))
.OnProperty(g => g.Description).Use(new Lipsum(LipsumFlavor.InDerFremde));
var starFiller = new Filler <Star>();
starFiller.Setup()
.OnProperty(s => s.Id).IgnoreIt()
.OnProperty(s => s.Galaxy).IgnoreIt()
.OnProperty(s => s.GalaxyId).IgnoreIt()
.OnProperty(s => s.Name).Use(new RealNames(NameStyle.FirstName))
.OnProperty(s => s.DiscoveryDate).Use(new DateTimeRange(DateTime.Now.AddYears(-300), DateTime.Now))
.OnProperty(s => s.Mass).Use(new DoubleRange(1000.0, 1000_000_000.0))
.OnProperty(s => s.DistanceToEarth).Use(new FloatRange(0.1f, 1000_000_000.0f))
.OnProperty(s => s.Description).Use(new Lipsum(LipsumFlavor.InDerFremde));
var galaxies = galaxyFiller.Create(100);
var random = new Random();
foreach (var g in galaxies)
{
var stars = starFiller.Create(random.Next(10, 150));
foreach (var s in stars)
{
g.Stars.Add(s);
}
}
using (var context = new LostStarsDbContext())
{
context.Galaxies.AddRange(galaxies);
await context.SaveChangesAsync();
Console.WriteLine("Save complete...");
}
}
private static void IQueryable()
{
using (var context = new LostStarsDbContext())
{
context.Database.Log = Console.WriteLine;
var galaxyQuery = context.Galaxies.Where(g => g.DiscoveryDate.Year > 1900);
galaxyQuery = galaxyQuery.OrderBy(g => g.Name);
galaxyQuery = galaxyQuery.Where(g => g.DiscoveryDate.Year < 1950);
//galaxyQuery = galaxyQuery.Where(g => g.Stars.Count() < 30);
var galaxies = galaxyQuery.ToList();
foreach (var g in galaxies)
{
Console.WriteLine($"{g.Name,-11} | {g.Form,-10} | {g.DiscoveryDate.Year}");
}
}
}
private static void EagerLoading()
{
using (var context = new LostStarsDbContext())
{
//var galaxies = context.Galaxies.Include("Stars").Take(20);
// wichtig: using System.Data.Entity;
var galaxies = context.Galaxies.Include(g => g.Stars).Take(20);
foreach (var galaxy in galaxies)
{
Console.WriteLine($"{galaxy.Name} | {galaxy.Form}");
foreach (var s in galaxy.Stars)
{
Console.WriteLine($"\t{s.Name} - ist {s.DistanceToEarth} Lichtjahre entfernt.");
}
}
}
}
private static void PreLoading()
{
using (var context = new LostStarsDbContext())
{
context.Stars.Where(s => s.GalaxyId == 1).ToList();
// 100 Stars werden im context gecached.
// weil die Stars für diese Galaxy bereits im context gecached sind,
// werden die Navigationsproperties automatisch richtig initialisiert
// ! nur bei 1-N Verbindungen !
// genannt: Relationship Fixup
var galaxy = context.Galaxies.Single(g => g.Id == 1);
Console.WriteLine($"{galaxy.Name} | {galaxy.Form}");
foreach (var s in galaxy.Stars)
{
Console.WriteLine($"\t{s.Name} - ist {s.DistanceToEarth} Lichtjahre entfernt.");
}
}
}
private static void ChangeTracker()
{
using (var context = new LostStarsDbContext())
{
context.Stars.First(); // Initialize Query
context.Database.Log = Console.WriteLine;
var galaxies = context.Galaxies.Take(10).ToList();
var firstGalaxy = galaxies[0];
var secondGalaxy = galaxies[1];
firstGalaxy.Name = "Franx Xaver Gruber";
context.Galaxies.Add(new Galaxy());
context.Galaxies.Remove(secondGalaxy);
Console.WriteLine($"{context.ChangeTracker.Entries<Galaxy>().Count()} Entries in ChangeTracker");
foreach (var entry in context.ChangeTracker.Entries <Galaxy>())
{
Console.WriteLine(entry.State);
}
Console.WriteLine("The modified once:");
foreach (var entry in context.ChangeTracker.Entries <Galaxy>().Where(e => e.State == EntityState.Modified))
{
foreach (var p in entry.OriginalValues.PropertyNames.Where(n => n != "Description"))
{
Console.WriteLine($"\tCurrent {p,-13}: {entry.CurrentValues.GetValue<object>(p)}");
Console.WriteLine($"\tOriginal {p,-13}: {entry.OriginalValues.GetValue<object>(p)}");
}
}
//context.SaveChanges();
}
}
private static void LazyLoading()
{
using (var context = new LostStarsDbContext())
{
// Voraussetzungen für Lazy Loading
// - Model Klassen Public
// - Navigationsproperties virtual
// - context.Configuration.LazyLoadingEnabled = true; // kann auch im Konstruktor passieren
context.Configuration.LazyLoadingEnabled = true; // Default: true
var galaxies = context.Galaxies.Take(20); //
// //
foreach (var galaxy in galaxies) // // // -> N + 1 Problem
{ // //
Console.WriteLine($"{galaxy.Name} | {galaxy.Form}"); //
foreach (var s in galaxy.Stars)
{
Console.WriteLine($"\t{s.Name} - ist {s.DistanceToEarth} Lichtjahre entfernt.");
}
}
}
}
private static void AsNoTracking()
{
using (var context = new LostStarsDbContext())
{
var stars = context.Stars.AsNoTracking().Take(10).ToList();
Console.WriteLine($"{context.ChangeTracker.Entries().Count()} Entries in Changetracker");
foreach (var s in stars)
{
Console.WriteLine(s.Name);
}
var firstStar = stars[0];
firstStar.Name = "The new name";
context.Stars.Attach(firstStar);
Console.WriteLine($"{context.ChangeTracker.Entries().Count()} Entries in Changetracker");
Console.WriteLine(context.Entry(firstStar).State);
//context.Entry(firstStar).State = EntityState.Modified;
context.Entry(firstStar).Property(s => s.Name).IsModified = true;
}
}