NHibernate和版本控制(时间戳) [英] NHibernate and versioning (timestamp)

问题描述

我有这个例外

在System.Convert.ToDateTime(对象值)上
在NHibernate.Type.DateTimeType.Get(IDataReader rs，Int32索引)中位于p:\ nhibernate-core \ src \ NHibernate \ Type \ DateTimeType.cs:line 43

at System.Convert.ToDateTime(Object value)
at NHibernate.Type.DateTimeType.Get(IDataReader rs, Int32 index) in p:\nhibernate-core\src\NHibernate\Type\DateTimeType.cs:line 43

我猜测系统尝试将行版本转换为日期时间时发生了错误

I guess the error occured when system trying to convert rowversion to datetime

这是我获取列表的方法

public static IList<Employee> getEmployees()
{
    using (ISession mySession = SessionFactory().OpenSession())
    {
        using (ITransaction myTransaction = mySession.BeginTransaction())
        {
            return mySession.CreateCriteria<Employee>().List<Employee>();
        }
    }
}

这是我的课程

public class Employee {
    private int _id;
    private Rank _rank;
    private string _visa;
    private string _firstName;
    private string _lastName;
    private string _university;
    private DateTime _rowversion;
    public Employee() {
        EmployeeFunctionInProject = new List<EmployeeFunctionInProject>();
        Group = new List<Group>();
    }
    public virtual int Id {
        get {
            return this._id;
        }
        set {
            this._id = value;
        }
    }
    public virtual Rank Rank {
        get {
            return this._rank;
        }
        set {
            this._rank = value;
        }
    }
    public virtual string Visa {
        get {
            return this._visa;
        }
        set {
            this._visa = value;
        }
    }
    public virtual string FirstName {
        get {
            return this._firstName;
        }
        set {
            this._firstName = value;
        }
    }
    public virtual string LastName {
        get {
            return this._lastName;
        }
        set {
            this._lastName = value;
        }
    }
    public virtual string University {
        get {
            return this._university;
        }
        set {
            this._university = value;
        }
    }
    public virtual DateTime Rowversion {
        get {
            return this._rowversion;
        }
        set {
            this._rowversion = value;
        }
    }
    public virtual IList<EmployeeFunctionInProject> EmployeeFunctionInProject { get; set; }
    public virtual IList<Group> Group { get; set; }
}

这是我的地图

<hibernate-mapping assembly="MyWeb11" namespace="MyWeb11.Models" xmlns="urn:nhibernate-mapping-2.2">
  <class name="Employee" table="EMPLOYEE" lazy="true" >
    <id name="Id" column="ID">
      <generator class="identity" />
    </id>
    <many-to-one name="Rank">
      <column name="RANK" sql-type="int" not-null="true" />
    </many-to-one>
    <property name="Visa">
      <column name="VISA" sql-type="varchar" not-null="true" unique="true" />
    </property>
    <property name="FirstName">
      <column name="FIRST_NAME" sql-type="varchar" not-null="true" />
    </property>
    <property name="LastName">
      <column name="LAST_NAME" sql-type="varchar" not-null="true" />
    </property>
    <property name="University">
      <column name="UNIVERSITY" sql-type="varchar" not-null="true" />
    </property>
    <property name="Rowversion">
      <column name="ROWVERSION" sql-type="timestamp" not-null="true" />
    </property>
    <bag name="EmployeeFunctionInProject" inverse="true">
      <key column="EMPLOYEE" />
      <one-to-many class="EmployeeFunctionInProject" />
    </bag>
    <bag name="Group" inverse="true">
      <key column="LEADER" />
      <one-to-many class="Group" />
    </bag>
  </class>
</hibernate-mapping>

我已经搜索了一种解决方案，但没有找到解决方案.任何帮助表示赞赏.预先感谢！

I have searched for a solution but haven't found one. Any help is appreciated. Thanks in advance!

推荐答案

我希望您使用的是SQL Server，其中timestamp不是DateTime值.没有任何共同之处.请参阅(最新名称为rowversion)-行版本号(Transact -SQL)

I would expect that you are using SQL Server, where timestamp is not a DateTime value. Nothing in common. See (the up-to-date name is rowversion) - rowversion (Transact-SQL)

是一种数据类型，它公开了数据库中自动生成的唯一二进制数. 行版本通常用作对表行进行版本标记的机制.存储大小为8个字节. 行版本数据类型只是一个递增数字，并不保留日期或时间.要记录日期或时间，请使用 datetime2 数据类型.

Is a data type that exposes automatically generated, unique binary numbers within a database. rowversion is generally used as a mechanism for version-stamping table rows. The storage size is 8 bytes. The rowversion data type is just an incrementing number and does not preserve a date or a time. To record a date or time, use a datetime2 data type.

我的建议是，与<version>属性的NHiberante结合使用，确实像您一样使用这种类型的列(行版本/时间戳).参见:

What I would suggest, do use that type of column (rowversion/timestamp) as you did, with conjunction of NHiberante power of <version> attribute. See:

• 5.1.7.版本(可选)
• Ayende NHibernate映射-并发

• 5.1.7. version (optional)
• Ayende NHibernate Mapping - Concurrency

有一个映射片段:

<version name="Timestamp " generated="always"
         unsaved-value="null" type="BinaryBlob">
    <column name="Version" not-null="false"
            sql-type="timestamp"/>
</version>

如果我们需要将该二进制内容传递给客户端，我们可以将其转换为字符串属性，请参见:

If we need to pass that binary stuff to client we can do some conversion into string property, see:

• NHibernate中会话外的乐观并发性

作为C#代码的属性:

protected virtual byte[] Timestamp { get; set; }
public virtual string Version
{
    get { return Timestamp.IsEmpty() ? null : Convert.ToBase64String(Timestamp); }
    set { Timestamp = value.IsEmpty() ? null : Convert.FromBase64String(value); }
}

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