public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Stock { get; set; }

    [Timestamp]
    public byte[] RowVersion { get; set; } = null!;
}

// Usage
try
{
    product.Stock -= quantity;
    await context.SaveChangesAsync();
}
catch (DbUpdateConcurrencyException)
{
    // Someone else modified the record — re-read and retry
    var entry = ex.Entries.Single();
    await entry.ReloadAsync();
    // merge logic...
}