zoukankan      html  css  js  c++  java
  • Lerning Entity Framework 6 ------ Handling concurrency With SQL Server Database


    The default Way to handle concurrency of Entity Framework is using optimistic concurrency. When two clinets update the same entity, one of theirs data will be lost without any notify.

    Some times, the client want to know if his data has been saved successful, so, we have to do some Extra work:

    • Create a project named ConcurrencyTest

    • Add a entity:

        public class Person
        {
            public int PersonId { get; set; }
      
            public string Name { get; set; }
      
            public byte[] RowVersion { get; set; }
        }
      

    Please take attention to the RowVersion property. It used to record the version of the data row in a table.

    Add fluent API codes:

        public class PersonMap : EntityTypeConfiguration<Person>
        {
            public PersonMap()
            {
                Property(p => p.RowVersion)
                    .IsFixedLength()
                    .HasMaxLength(8)
                    .HasDatabaseGeneratedOption(System.ComponentModel.DataAnnotations.Schema.DatabaseGeneratedOption.Computed)
                    .IsRowVersion();
            }
        }
    
    • Add a DbContext:

        public class MyContext:DbContext
        {
            public DbSet<Person> People { get; set; }
      
            protected override void OnModelCreating(DbModelBuilder modelBuilder)
            {
                base.OnModelCreating(modelBuilder);
                modelBuilder.Configurations.Add(new PersonMap());
            }
        }
      
    • Add some test codes:

        static void Main(string[] args)
        {
            AddPerson();
            DoConcurrentcyTest();
      
            Console.Read();
        }
      
        static void DoConcurrentcyTest()
        {
            using (MyContext db1 = new MyContext())
            {
                Person p1 = db1.People.Find(1);
      
                using (MyContext db2 = new MyContext())
                {
                    Person p2 = db2.People.Find(1);
                    p2.Name = "Ross";
                    db2.SaveChanges();
                }
      
                p1.Name = "Monnica";
                try
                {
                    db1.SaveChanges();
                }
                catch (DbUpdateConcurrencyException)
                {
                    Console.WriteLine("please refresh it");
                }
            }
        }
      

    When you save the person entity, if someone have changed it after you get, a DbUpdateConcurrencyException will be trowed.

    That's all.

  • 相关阅读:
    置换及Polya定理
    题解 UVa10943
    Error applying site theme: A theme with the name "Jet 1011" and version already exists on the server.
    用shtml来include网页文件
    SQL 2005 附加数据库出错"解决方法
    SVN 配置 入门教程
    Oracle .Net Develoer
    JdbcTemplate完全学习
    SVD外积展开式
    初识 Nslookup 命令
  • 原文地址:https://www.cnblogs.com/zzy0471/p/6911370.html
Copyright © 2011-2022 走看看