乐观并发：IsConcurrencyToken和RowVersion [英] Optimistic concurrency: IsConcurrencyToken and RowVersion

问题描述

我正在创建我应用程序中使用的默认并发策略。

我决定采取乐观的策略。

我的所有实体都被映射为 Table type（TPT）（使用继承）。我很快就了解到，在Entity Framework中使用RowVersion类型的继承性列出现问题：

  Product 
 
 ID INT IDENTITY PRIMARY KEY 
 RowVersion ROWVERSION 
 
 Car（继承产品记录）
 
颜色TYNIINT NOT NULL，
 AnotherProperty .... 
  

如果我更新了 Car的记录从 Product 表中的RowVersion列表将不会更新。

我打算使用一个类型为<$ 产品中的c $ c> datetime2（7），如果修改了继承此表的表的任何记录，则手动更新。 >

我想我正在重塑轮子。

有另一种方式使用乐观并发策略与 ROWVERSION 在实体框架中使用表类型（TPT）

修改

我的映射：

  class Product 
 {
 int Id {get;组; } 
 string Name {get;组; } 
 byte [] RowVersion {get;组; } 
} 
 
 class Car：Product 
 {
 int Color {get;组; 
} 
  

CodeFirst 约定。 b
$ b

只有产品实体上的RowVersion属性具有自定义定义：

  modelBuilder.Entity< Product>（）
 .Property（t => t.RowVersion）
 .IsConcurrencyToken（）; 
  

解决方案

你必须使用映射

  modelBuilder.Entity< Product>（）
 .Property（t => t.RowVersion）
 .IsRowVersion（）; // Not：IsConcurrencyToken 
  

IsConcurrencyToken 将属性配置为并发令牌，但是（当用于 byte [] 属性时）

• 数据类型是nvarchar（max）


• 如果不初始化它，它的值始终为null


• 当它的记录是更新。

IsRowVersion

• 有数据类型 rowversion （在Sql Server中，或 timestamp 在早期版本中），所以


• 其值永远不为空，并且


• 当更新记录时，其值始终自动递增。 / li>
  
• ，它会自动将属性配置为乐观的con货币令牌

现在，当您更新 Car 时，您会看到两个更新语句：

  DECLARE @p int 
更新[dbo] 
 SET @p = 0 
 WHERE（（[Id] = @ 0）AND（[Rowversion] = @ 1））
 SELECT [Rowversion] 
 FROM [dbo] [产品] 
 WHERE @@ ROWCOUNT> 0 AND [Id] = @ 0 
 
更新[dbo]。[Car] 
 SET ... 
  

第一个语句不会更新任何东西，但它会增加rowversion，如果rowversion在其间进行更改，它将引发并发异常。

顺便说一下， IsRowVersion 相当于 [Timestamp] 属性：

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

I'm creating the default concurrency strategy that I will use in my application.

I decided for an optimistic strategy.

All of my entities are mapped as Table per Type (TPT) (using inheritance). I soon learned that there is a problem when using columns of type RowVersion with inheritance on Entity Framework:

Product

Id INT IDENTITY PRIMARY KEY
RowVersion ROWVERSION

Car (inherits Product records)

Color TYNIINT NOT NULL,
AnotherProperty....   

If I update a record of the Car table the RowVersion column from Product table will not be updated.

I plan to use a column of type datetime2 (7) in Product and update it manually if any records of the tables that inherit this table are modified.

I think I'm reinventing the wheel.

Is there another way to use the optimistic concurrency strategy with ROWVERSION when using Table per Type (TPT) in Entity Framework?

Edit

My mapping:

class Product
{
    int Id { get; set; }
    string Name { get; set; }
    byte[] RowVersion { get; set; }
}

class Car : Product
{
    int Color { get; set; }
}

CodeFirst conventions.

Only the RowVersion property on Product entity has custom definitions:

modelBuilder.Entity<Product>() 
    .Property(t => t.RowVersion) 
    .IsConcurrencyToken();

解决方案

You have to use the mapping

modelBuilder.Entity<Product>() 
.Property(t => t.RowVersion) 
.IsRowVersion(); // Not: IsConcurrencyToken

IsConcurrencyToken does configure a property as concurrency token, but (when using it for a byte[] property)

• the data type is nvarchar(max)
• its value is always null if you don't initialize it
• its value is not auto-incremented when a record is updated.

IsRowVersion on the other hand,

• has datatype rowversion (in Sql Server, or timestamp in earlier versions), so
• its value is never null, and
• its value is always auto-incremented when a record is updated.
• and it automatically configures the property to be an optimistic concurrency token.

Now when you update a Car you'll see two update statements:

DECLARE @p int
UPDATE [dbo].[Product]
SET @p = 0
WHERE (([Id] = @0) AND ([Rowversion] = @1))
SELECT [Rowversion]
FROM [dbo].[Product]
WHERE @@ROWCOUNT > 0 AND [Id] = @0

UPDATE [dbo].[Car]
SET ...

The first statement doesn't update anything, but it increments the rowversion, and it will throw a concurrency exception if the rowversion changed in-between.

By the way, IsRowVersion is equivalent to the [Timestamp] attribute:

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

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