Entity Framework Core Concurrency (edit)

• Pessimistic Concurrency
• Optimistic Concurrency
• Entity Framework Core provides support for optimistic concurrency management
• Concurrency Token vs Timestamp (RowVersion)
• Concurrency Conflict
• Concurrency using xmin
• Usage of xmin column as concurrency token

Implementing optimistic concurrency with EF Core (dzimchuk.net)

• Optimistic Concurrency

Concurrency Management in Entity Framework Core | Learn Entity Framework Core

• Pessimistic Concurrency
• Optimistic Concurrency

Concurrency (entityframeworkcore.com)

The Code Blogger - Implement optimistic concurrency with .NET EF Core

Handling Concurrency in EF-Core - Learn Entity Framework Core 5

Current values: The present values that were last updated into the database by the user.
Original Values: The value that was present in the database initially, before concurrency occurred.
Database Value: The values that are currently stored in the database.

Giá trị hiện tại: Giá trị hiện tại được người dùng cập nhật lần cuối vào cơ sở dữ liệu.
Giá trị gốc: giá trị có trong cơ sở dữ liệu ban đầu, trước khi xảy ra đồng thời.
Giá trị cơ sở dữ liệu: Các giá trị hiện đang được lưu trữ trong cơ sở dữ liệu.

PostgreSQL

c# - How to use EF Core concurrency token created by ForNpgsqlUseXminAsConcurrencyToken - Stack Overflow

The PostgreSQL xmin system column

Concurrency Tokens | Npgsql Documentation

protected override void OnModelCreating(ModelBuilder modelBuilder)
    => modelBuilder.Entity<Blog>()
                   .UseXminAsConcurrencyToken();

class Blog
{
    ...
    public uint xmin { get; set; }
}

PartsUnlimited : Optimistic Concurrency with PostgreSQL source (microsoft.github.io)

[SOLVED] => EF Core Postgres DbUpdateConcurrencyException when... (entityframeworkcore.com)

Usage of xmin column as concurrency token · Issue #19 · npgsql/efcore.pg (github.com)

Concurrency using xmin · Issue #179 · npgsql/efcore.pg (github.com)

modelBuilder.Entity<Person>().UseXminAsConcurrencyToken();

using System;
using Microsoft.EntityFrameworkCore;

namespace DataSetSerialization
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var fooId = Guid.NewGuid();

            using (var context = new TestContext())
            {
                context.Add(new Person
                {
                    Id = fooId,
                    Name = "Foo",
                });

                context.SaveChanges();
            }

            using (var context = new TestContext())
            {
                var wes = context.Find<Person>(fooId);
                wes.Name = "Bar";

                context.Entry(wes).Property(x => x.XMin).OriginalValue = (uint) 1;

                // context.SaveChanges throws DbUpdateConcurrencyException
                context.SaveChanges();
            }
        }
    }

    internal class TestContext : DbContext
    {
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseNpgsql("User ID=postgres;Password=xxxx;Host=localhost;Port=5432;Database=test;Pooling=true;");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Person>(b =>
            {
                b.Property(x => x.XMin)
                    .HasColumnName("xmin")
                    .HasColumnType("xid")
                    .ValueGeneratedOnAddOrUpdate()
                    .IsConcurrencyToken();
            });

            base.OnModelCreating(modelBuilder);
        }
    }

    public class Person
    {
        public Guid Id { get; set; }
        public string Name { get; set; }

        public uint XMin { get; set; }
    }
}