实体框架并发savechanges死锁 [英] Entity framework concurrent savechanges deadlock
问题描述
我正在编写一个非常简单的多用户WPF应用程序，每个用户都可以修改/删除自己的数据。表示每个用户可以查看其他用户的所有数据，但不允许修改或删除它。整个应用程序运行良好，直到2个或更多客户端同时点击savechanges方法，然后我有时会遇到数据库死锁。
事务（进程ID 57）已死锁锁定资源与另一个进程，并已被选为死锁受害者。重新运行该事务。
我不知道为什么会出现这种死锁，因为不可能由不同的用户同时修改或删除相同的数据。
我写了一个简短的程序来证明这种行为。最后的删除方法模拟两个用户同时删除自己的数据。
这是我的DbContext和Datamodel：
public class 上下文：DbContext
{
public DbSet< City> dbsCities { get ; set ; }
public DbSet< House> dbsHouses { get ; set ; }
public DbSet< Person> dbsPersons { get ; set ; }
public Context（）： base （ @ Server = .\SQLExpress; Database = test; Trusted_Connection = Yes; Connection Timeout = 5）
{
Configuration.AutoDetectChangesEnabled = true ;
Configuration.LazyLoadingEnabled = false ;
Configuration.ProxyCreationEnabled = false ;
}
受保护 覆盖 void OnModelCreating（DbModelBuilder modelBuilder）
{
modelBuilder.Entity< City>（）。HasMany（c = > c.Houses）.WithRequired（c = > c.City）.WillCascadeOnDelete（ true ）;
modelBuilder.Entity< House>（）。HasMany（p = > p.Residents）.WithRequired（p = > p.House）.WillCascadeOnDelete（ true ）;
}
}
public class City
{
public Guid Id { get ; set ; }
public string 名称{ get ; set ; }
public virtual ICollection< House>房屋{获取; set ; }
public City（）
{
Id = Guid.NewGuid（）;
Houses = new List< House>（）;
}
}
public class House
{
public Guid Id { get ; set ; }
public int Number { get ; set ; }
public string 代码{ get ; set ; }
public virtual City City {获得; set ; }
public virtual ICollection< Person>居民{获取; set ; }
public House（）
{
Id = Guid.NewGuid（）;
Residents = new List< Person>（）;
}
}
public class Person
{
public Guid Id { get ; set ; }
public string 名字{ get ; set ; }
public string 姓氏{ get ; set ; }
public virtual House House {获得; set ; }
public Person（）
{
Id = Guid.NewGuid（）;
}
}
这里生成testdata的代码：
< span class =code-keyword> using （Context ctx = new Context（））
{
List< City> cities = new 列表< City>（）{ new City（）{Name = 纽约}};
for （ int h = 1 ; h < = 50 ; h ++）
{
string code = A ;
if （h％ 2 == 0 ）
code = B;
House house = new House（）{Number = h，Code = code};
cities [ 0 ]。Houses.Add（house）;
for （ int i = 0 ; i < = 100 ; i ++）
house.Residents.Add（< span class =code-keyword> new Person（）{Firstname = A，Lastname = B}）;
}
ctx.dbsCities.AddRange（cities）;
ctx.SaveChanges（）;
}
最后导致死锁的方法
私有 void 删除（对象发件人，RoutedEventArgs e）
{
string [] to = new string [] { A， B};
Parallel.ForEach（to，code = >
{
DeleteHouses（code）;
}）;
}
private void DeleteHouses（ string 代码）
{
使用（ var ctx = new Context（））
{
ctx.Database.Log + = Console.WriteLine;
var todel = ctx.dbsHouses.Where（d => d.Code == code）;
if （todel！= null ）
{
ctx。 dbsHouses.RemoveRange（todel）;
ctx.SaveChanges（）;
}
}
}
我尝试了什么：
我尝试过使用一个使用IsolationLevel Snapshot的TransactionScope，这在其他一些论坛帖子中推荐使用
但没有成功。
无论如何，我认为它与IsolationLevel无关，因为我的查询正在删除
不同的行。
< blockquote>谁告诉你使用并行编程？
我现在可以看到为什么EF会说糟糕的说唱。
用保存更改等方式敲击系统
您需要回归基础知识。
c＃ - Parallel不适用于实体框架 - Stack Overflow [ ^ ]
I am writing a quite simple Multiuser WPF application where each user can modify / delete his own data. Means each user can see all the data of other users but is not allowed to modify or delete it. The whole application performs well until 2 or more clients hit the savechanges method at the same time, then i sometimes run into a Database Deadlock.
Transaction (Process ID 57) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.
I have no idea why it comes to that deadlock, as it is not possible that the same data is modified or deleted at the same time by different users.
I wrote a short program that demonstates the behaviour. The delete method at the end simulates two users deleting their own data at the same time.
Here is my DbContext and Datamodel:
public class Context : DbContext
{
public DbSet<City> dbsCities { get; set; }
public DbSet<House> dbsHouses { get; set; }
public DbSet<Person> dbsPersons { get; set; }
public Context() : base(@"Server=.\SQLExpress;Database=test;Trusted_Connection=Yes;Connection Timeout=5")
{
Configuration.AutoDetectChangesEnabled = true;
Configuration.LazyLoadingEnabled = false;
Configuration.ProxyCreationEnabled = false;
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<City>().HasMany(c => c.Houses).WithRequired(c => c.City).WillCascadeOnDelete(true);
modelBuilder.Entity<House>().HasMany(p => p.Residents).WithRequired(p => p.House).WillCascadeOnDelete(true);
}
}
public class City
{
public Guid Id { get; set; }
public string Name { get; set; }
public virtual ICollection<House> Houses { get; set; }
public City()
{
Id = Guid.NewGuid();
Houses = new List<House>();
}
}
public class House
{
public Guid Id { get; set; }
public int Number { get; set; }
public string Code { get; set; }
public virtual City City { get; set; }
public virtual ICollection<Person> Residents { get; set; }
public House()
{
Id = Guid.NewGuid();
Residents = new List<Person>();
}
}
public class Person
{
public Guid Id { get; set; }
public string Firstname { get; set; }
public string Lastname { get; set; }
public virtual House House { get; set; }
public Person()
{
Id = Guid.NewGuid();
}
}
And here the code to generate testdata:
using (Context ctx = new Context())
{
List<City> cities = new List<City>() { new City() { Name = "New York" } };
for (int h = 1; h <= 50; h++)
{
string code = "A";
if (h % 2 == 0)
code = "B";
House house = new House() {Number = h, Code = code };
cities[0].Houses.Add(house);
for (int i = 0; i <= 100; i++)
house.Residents.Add(new Person() { Firstname = "A", Lastname = "B" });
}
ctx.dbsCities.AddRange(cities);
ctx.SaveChanges();
}
Finally the Method that causes the deadlock
private void Delete(object sender, RoutedEventArgs e)
{
string[] to = new string[] {"A", "B"};
Parallel.ForEach(to, code =>
{
DeleteHouses(code);
});
}
private void DeleteHouses(string code)
{
using (var ctx = new Context())
{
ctx.Database.Log += Console.WriteLine;
var todel = ctx.dbsHouses.Where(d=>d.Code == code);
if (todel != null)
{
ctx.dbsHouses.RemoveRange(todel);
ctx.SaveChanges();
}
}
}
What I have tried:
I have tried using a TransactionScope using IsolationLevel Snapshot which was
recommended in some other forum posts without success.
Anyway i think it has nothing to do with the IsolationLevel as my queries are deleting
different rows.
Who told you to use "parallel" programming?
I can see now why EF gets a bad rap.
Hammering the system with "Save Changes", etc.
You need to get back to basics.
c# - Parallel doesnt work with Entity Framework - Stack Overflow[^]
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