乐观并发：IsConcurrencyToken和RowVersion

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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。

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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