在Model First方法中使用Timestamp属性的EF并发处理 [英] EF Concurrency Handling with Timestamp attribute in Model First approach

问题描述

我试图实现使用ASP.NET MVC应用程序中的实体框架处理并发性

I am trying to implement the solution given in Handling Concurrency with the Entity Framework in an ASP.NET MVC Application .

文章说：

向部门实体添加跟踪属性

在Models\Department.cs中，添加跟踪属性：

Adding a Tracking Property to the Department Entity

In Models\Department.cs, add a tracking property:

[Timestamp] 
public Byte[] Timestamp { get; set; }

Timestamp属性指定此列将包含在发送的更新和删除命令的Where子句中到数据库。

The Timestamp attribute specifies that this column will be included in the Where clause of Update and Delete commands sent to the database.

由于我使用的是模型，方法，我遵循步骤1 - 5概述在使用实体框架创建时间戳列

Since I'm using a model first approach, I followed steps 1 - 5 outlined in Creating a Timestamp column with Entity Framework

1. 在EF模型中向实体添加名为Timestamp的属性


2. 设置将类型转换为二进制


3. 将可空值设置为false


4. 将StoreGeneratedPattern设置为Computed


5. 将并发模式设置为Fixed

1. Add a property named "Timestamp" to the entity in EF’s model
2. Set the type to binary
3. Set nullable to false
4. Set StoreGeneratedPattern to Computed
5. Set ConcurrencyMode to Fixed

当我从数据库模型更新代码时，Models\Department.cs现在包含

When I update my code from the database model, the Models\Department.cs now contains

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

然后我使用元数据类来指定Timestamp属性：

Then I used the metadata class to specify the Timestamp attribute:

// Metadata for Department entity
public class DepartmentMetadata
{
    [Timestamp]
    public byte Timestamp { get; set; }
}

Q1。我测试了在行编辑的情况下， Timestamp 列正在更改。不是

Q1. I tested whether the value of the Timestamp column is changing in case of row edits. It isn't.

编辑1 问题是因为SQL Server列类型为 binary 应该是它的类型为 timestamp 。

EDIT 1 The problem was caused because the SQL Server column type was binary, where it should have been of type timestamp. Changing the data type fixed the issue of the Timestamp column not getting updated.

Q2。我正在尝试修改相同的实体（使用在新选项卡中打开），以查看是否抛出了 OptimisticConcurrencyException 。不是我究竟做错了什么？请帮助我理解，谢谢。

Q2. I was trying to modify the same entity (using "Open in new tab") to see if an OptimisticConcurrencyException is thrown. It isn't. What am I doing wrong? Please help me understand, thanks.

推荐答案

问题是因为我每个HTTP会话有一个ObjectContext，因此，打开一个新的选项卡并进行测试将不导致并发异常。

The problem was caused because I had one ObjectContext per HTTP session, and so opening a new tab and testing it would NOT cause a concurrency exception.

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