Optymistyczna współbieżność w EF Core

2022-03-31T21:52:04+02:00

Jest jeszcze IsConcurrencyToken() – nadałby się do powyższego scenariusza?

2022-04-02T07:33:22+02:00

Tak można również wykorzystać IsConcurrencyToken, szczególnie jak już mamy jakąś kolumnę, która aktualizujemy z każdą zmianą rekordu w bazie.

	public class Product
	{
	public Guid Id { get; set; } = Guid.NewGuid();

	public string Name { get; set; }

	public decimal Price { get; set; }
	}

	public class DataContext : DbContext
	{
	protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
	{
	optionsBuilder.UseSqlServer(@"Server=.\SQLEXPRESS;Database=EFCoreOptimisticConcurrency;Trusted_Connection=True;");
	}

	public DbSet<Product> Products { get; set; }
	}

	private static async Task Setup(Guid productId)
	{
	await using var db = new DataContext();

	var product = await db.Products.FirstOrDefaultAsync(p => p.Id == productId);

	if (product == null)
	{
	product = new Product()
	{
	Id = productId
	};

	await db.Products.AddAsync(product);
	}

	product.Name = "product";
	product.Price = 10;

	await db.SaveChangesAsync();
	}

	private static async Task EditProduct(Guid productId, Action<Product> editAction, int delay)
	{
	await using var db = new DataContext();

	var product = await db.Products.FirstOrDefaultAsync(p => p.Id == productId);

	await Task.Delay(delay);

	editAction(product);

	await db.SaveChangesAsync();
	}

	static async Task Main(string[] args)
	{
	var productId = Guid.Parse("E440B325-AD1F-4B4D-9162-36DFB0F3A357");

	await Setup(productId);

	var tasks = new[]
	{
	EditProduct(productId, p => p.Price = 11, 1000),
	EditProduct(productId, p => p.Price = 12, 100)
	};

	await Task.WhenAll(tasks);

	var product = await GetProduct(productId);

	Console.WriteLine($"Product: {product.Name}, price: {product.Price}");
	}

PROGRAMUJE .NET – Daniel Plawgo

	EditProduct(productId, p => p.Price = 11, 1000),
	EditProduct(productId, p => p.Name = "new product", 100)

	public class ProductEntityTypeConfiguration : IEntityTypeConfiguration<Product>
	{
	public void Configure(EntityTypeBuilder<Product> builder)
	{
	builder.Property(p => p.RowVersion)
	.IsRowVersion();
	}
	}

	private static async Task EditProduct(Guid productId, Action<Product> editAction, int delay)
	{
	await using var db = new DataContext();

	try
	{
	var product = await db.Products.FirstOrDefaultAsync(p => p.Id == productId);

	await Task.Delay(delay);

	editAction(product);

	await db.SaveChangesAsync();
	}
	catch (DbUpdateConcurrencyException ex)
	{
	foreach (var entry in ex.Entries)
	{
	var databaseValues = await entry.GetDatabaseValuesAsync();

	foreach (var property in entry.CurrentValues.Properties)
	{
	var proposedValue = entry.CurrentValues[property];
	var databaseValue = databaseValues[property];
	var originalValue = entry.OriginalValues[property];

	if (proposedValue.Equals(databaseValue) \|\| originalValue.Equals(databaseValue) \|\| property.Name == "RowVersion")
	{
	continue;
	}

	Console.WriteLine($"ProposedValue: {proposedValue}, DatabaseValue: {databaseValue}, OriginalValue: {originalValue}.");

	//proposedValues[property] = wartość do zapisu;
	}

	entry.OriginalValues.SetValues(databaseValues);
	}
	}
	}