using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EFConcurrencyApp.Model
{
    public class News
    {
        public int Id { get; set; }
        [MaxLength(100)]
        public string Title { get; set; }
        [MaxLength(30)]
        public string Author { get; set; }
        public string Content { get; set; }
        public DateTime CreateTime { get; set; }
        public decimal Amount { get; set; }

    }
}

namespace EFConcurrencyApp.Migrations
{
    using EFConcurrencyApp.Model;
    using System;
    using System.Data.Entity;
    using System.Data.Entity.Migrations;
    using System.Linq;

    internal sealed class Configuration : DbMigrationsConfiguration<EFConcurrencyApp.EF.EFDbContext>
    {
        public Configuration()
        {
            AutomaticMigrationsEnabled = false;
        }

        protected override void Seed(EFConcurrencyApp.EF.EFDbContext context)
        {
            //  This method will be called after migrating to the latest version.

            //  You can use the DbSet<T>.AddOrUpdate() helper extension method
            //  to avoid creating duplicate seed data.

            context.News.AddOrUpdate(
                 new Model.News()
                 {
                     Title = "美國(guó)大城市房?jī)r(jià)太貴 年輕人靠“眾籌”買房",
                     Author = "佚名",
                     Content = "美國(guó)大城市房?jī)r(jià)太貴 年輕人靠“眾籌”買房",
                     CreateTime = DateTime.Now,
                     Amount = 0,
                 },
                 new Model.News()
                 {
                     Title = "血腥撲殺流浪狗太殘忍？那提高成本就是必須的代價(jià)",
                     Author = "佚名",
                     Content = "血腥撲殺流浪狗太殘忍？那提高成本就是必須的代價(jià)",
                     CreateTime = DateTime.Now,
                     Amount = 0,
                 },
                 new Model.News()
                 {
                     Title = "iPhone 8或9月6日發(fā)布 售價(jià)或1100美元起",
                     Author = "網(wǎng)絡(luò)",
                     Content = "iPhone 8或9月6日發(fā)布 售價(jià)或1100美元起",
                     CreateTime = DateTime.Now,
                     Amount = 0,
                 }
                 );
        }
    }
}

using EFConcurrencyApp.Model;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EFConcurrencyApp.EF
{
    public class EFDbContext:DbContext
    {
        public EFDbContext()
            : base("name=AppConnection")
        {

        }

        public DbSet<News> News { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // 設(shè)置表名和主鍵
            modelBuilder.Entity<News>().ToTable("News").HasKey(p => p.Id);
            base.OnModelCreating(modelBuilder);
        }
    }
}

static News FindNews(int id)
{
      using (var db = new EFDbContext())
      {
            return db.News.Find(id);
      }
}
static void UpdateNews(News news)
{
      using (var db = new EFDbContext())
      {
          db.Entry(news).State = EntityState.Modified;
          db.SaveChanges();
       }
}

//1.用戶甲獲取id=1的新聞
var news1 = FindNews(1);
//2.用戶乙獲取id=1的新聞
var news2 = FindNews(1);
//3.用戶甲更新這個(gè)實(shí)體的新聞標(biāo)題
news1.Title = news1.Title + "（更新）";
UpdateNews(news1);
//4.用戶乙更新這個(gè)實(shí)體的Amount
news2.Amount = 10m;
UpdateNews(news2);

static News GetUpdatedNews(int id, string title, string author, decimal amount, string content, DateTime createTime)
{
     return new News
     {
           Id = id,
           Title = title,
           Amount = amount,
           Author = author,
           Content = content,
           CreateTime = createTime,
      };
}

static void UpdateNewsEnhanced(News originalNews, News newNews)
{
            using (var db = new EFDbContext())
            {
                //從數(shù)據(jù)庫(kù)中檢索最新的模型
                var news = db.News.Find(originalNews.Id);
                //接下來檢查用戶修改的每個(gè)屬性
                if (originalNews.Title != newNews.Title)
                {
                    //將新值更新到數(shù)據(jù)庫(kù)
                    news.Title = newNews.Title;
                }
                if (originalNews.Content != newNews.Content)
                {
                    //將新值更新到數(shù)據(jù)庫(kù)
                    news.Content = newNews.Content;
                }
                if (originalNews.CreateTime != newNews.CreateTime)
                {
                    //將新值更新到數(shù)據(jù)庫(kù)
                    news.CreateTime = newNews.CreateTime;
                }
                if (originalNews.Amount != newNews.Amount)
                {
                    //將新值更新到數(shù)據(jù)庫(kù)
                    news.Amount = newNews.Amount;
                }
                if (originalNews.Author != newNews.Author)
                {
                    //將新值更新到數(shù)據(jù)庫(kù)
                    news.Author = newNews.Author;
                }
                // 持久化到數(shù)據(jù)庫(kù)
                db.SaveChanges();
            }
}

[Timestamp]
public byte[] RowVersion { get; set; }

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
      // 設(shè)置表名和主鍵
      modelBuilder.Entity<News>().ToTable("News").HasKey(p => p.Id);
      // 設(shè)置屬性
      modelBuilder.Entity<News>().Property(d => d.RowVersion).IsRowVersion();
      base.OnModelCreating(modelBuilder);
}

using (var context = new EFDbContext())
{
                var news = context.News.SingleOrDefault(p => p.Id == 1);
                Console.WriteLine(string.Format("標(biāo)題：{0} 打賞金額:{1} ", news.Title, news.Amount.ToString("C")));
                context.Database.ExecuteSqlCommand(@"update news set 
                        amount = 229.95 where Id = @p0", news.Id);
                news.Amount = 239.95M;
                Console.WriteLine(string.Format("標(biāo)題：{0} 打賞金額:{1} ", news.Title, news.Amount.ToString("C")));
                context.SaveChanges();
}

using (var context = new EFDbContext())
{
      var news = context.News.SingleOrDefault(p => p.Id == 1);
      Console.WriteLine(string.Format("標(biāo)題：{0} 打賞金額:{1} ", news.Title, news.Amount.ToString("C")));
      context.Database.ExecuteSqlCommand(string.Format(@"update News set 
                        Amount = 229.95 where Id = {0}", news.Id));
      news.Amount = 239.95M;
      Console.WriteLine(string.Format("標(biāo)題：{0} 打賞金額:{1} ", news.Title, news.Amount.ToString("C")));

      try
      {
            context.SaveChanges();
      }
      catch (DbUpdateConcurrencyException ex)
      {
            Console.WriteLine(string.Format("并發(fā)異常:{0}", ex.Message));
      }
      catch (Exception ex)
      {
            Console.WriteLine(string.Format("普通異常:{0}", ex.Message));
      }
}

using (var context = new EFDbContext())
{
      var news = context.News.SingleOrDefault(p => p.Id == 1);
      Console.WriteLine(string.Format("標(biāo)題：{0} 打賞金額:{1} ", news.Title, news.Amount.ToString("C")));
              
context.Database.ExecuteSqlCommand(string.Format(@"update News set 
       Amount = 229.95 where Id = {0}", news.Id));
       news.Amount = 239.95M;
       Console.WriteLine(string.Format("標(biāo)題：{0} 打賞金額:{1} ", news.Title, news.Amount.ToString("C")));       try
       {
         context.SaveChanges();
       }
       catch (DbUpdateConcurrencyException ex)
       {
          // 使用這段代碼會(huì)將Amount更新為239.95
          var postEntry = context.Entry(news);
          postEntry.OriginalValues.SetValues(postEntry.GetDatabaseValues());
          context.SaveChanges();
        }
        catch (Exception ex)
        {
           Console.WriteLine(string.Format("普通異常:{0}", ex.Message));
        }
}