实体框架 HierarchyId 解决方法

Question

英孚 5.0

我正在开发一个原型来一起测试hierarchyid 和实体框架。我有以下架构：

Create Table dbo.Employee
(
   EmployeeId int identity not null,
   Name nvarchar(100) not null,
   Node hierarchyid not null,
   NodePath as Node.ToString() persisted,
   Level AS Node.GetLevel() persisted,
   ManagerNode as Node.GetAncestor(1) persisted,
   ManagerNodePath as Node.GetAncestor(1).ToString() persisted
);

Alter Table dbo.Employee
    Add Constraint EmployeePK Primary Key NonClustered (EmployeeId);

Go

--Enforce Hierarchy
Alter Table dbo.Employee
    Add Constraint EmployeeManagerNodeNodeFK Foreign Key (ManagerNode) References Employee(Node);
Go

Create Unique Clustered Index EmployeeDepthFirstIndex on dbo.Employee(Node);

Go

Create NonClustered Index EmployeeBreathFirstIndex on dbo.Employee(Level, Node);

Go

根据我的阅读，EF 目前不支持 hierarchyid 数据类型，但有些人建议了一些解决方法，例如创建我在上面所做的计算列 (Node.ToString())。

有没有办法设置 EF 以便它识别父/子关系，以便我可以有效地拥有一个从属集合？例如

Employee.Subordinates

我唯一能想到的是创建一个带有 FK 的 ManagerId 列，但随后我将层次结构有效地存储在两个位置。

感谢您的帮助！

Answer 1

EF6 现在是开源的，所以很容易添加 HierarcyID 支持。我也加了。 您可以从 codeplex 下载修改后的源代码和编译/签名的 dll： http://entityframework.codeplex.com/SourceControl/network/forks/zgabi/efhierarchyidrc1（有时分叉名称会更改） 或来自 NuGet：https://www.nuget.org/packages/EntityFrameworkWithHierarchyId/ 当前 EF6 处于 RC1 状态，但我会将修改合并到 EF6 的每个更高版本。

我有以下型号：

public class Employee
{
    public int EmployeeId { get; set; }
    [Required, MaxLength(100)]
    public string Name { get; set; }
    [Required]
    public HierarchyId Node { get; set; }

    public IQueryable<Employee> GetSubordinates(MyContext context)
    {
        return context.Employees.Where(o => Node == o.Node.GetAncestor(1));
    }
}

public class MyContextInitializer : CreateDatabaseIfNotExists<MyContext>
{
    protected override void Seed(MyContext context)
    {
        context.Database.ExecuteSqlCommand(
            "ALTER TABLE [dbo].[Employees] ADD [ManagerNode] AS ([Node].[GetAncestor]((1))) PERSISTED");
        context.Database.ExecuteSqlCommand(
            "ALTER TABLE [dbo].[Employees] ADD CONSTRAINT [UK_EmployeeNode] UNIQUE NONCLUSTERED (Node)");
        context.Database.ExecuteSqlCommand(
            "ALTER TABLE [dbo].[Employees]  WITH CHECK ADD CONSTRAINT [EmployeeManagerNodeNodeFK] " +
            "FOREIGN KEY([ManagerNode]) REFERENCES [dbo].[Employees] ([Node])");
        context.Employees.Add(new Employee { Name = "Root", Node = new HierarchyId("/") });
        context.Employees.Add(new Employee { Name = "Emp1", Node = new HierarchyId("/1/") });
        context.Employees.Add(new Employee { Name = "Emp2", Node = new HierarchyId("/2/") });
        context.Employees.Add(new Employee { Name = "Emp3", Node = new HierarchyId("/1/1/") });
        context.Employees.Add(new Employee { Name = "Emp4", Node = new HierarchyId("/1/1/1/") });
        context.Employees.Add(new Employee { Name = "Emp5", Node = new HierarchyId("/2/1/") });
        context.Employees.Add(new Employee { Name = "Emp6", Node = new HierarchyId("/1/2/") });
    }
}

public class MyContext : DbContext
{
    public DbSet<Employee> Employees { get; set; }
}

生成的数据库：

CREATE TABLE [dbo].[Employees](
    [EmployeeId] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](100) NOT NULL,
    [Node] [hierarchyid] NOT NULL,
    [ManagerNode]  AS ([Node].[GetAncestor]((1))) PERSISTED,
 CONSTRAINT [PK_dbo.Employees] PRIMARY KEY CLUSTERED 
(
    [EmployeeId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY],
 CONSTRAINT [UK_EmployeeNode] UNIQUE NONCLUSTERED 
(
    [Node] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

ALTER TABLE [dbo].[Employees]  WITH CHECK ADD  CONSTRAINT [EmployeeManagerNodeNodeFK] FOREIGN KEY([ManagerNode])
REFERENCES [dbo].[Employees] ([Node])

获取 Emp1 员工子节点的示例：

    using (var c = new MyContext())
    {
        var firstItem = c.Employees.Single(o => o.Node == new HierarchyId("/1/"));

        foreach (var table1 in firstItem.GetSubordinates(c))
        {
            Console.WriteLine(table1.EmployeeId + " " + table1.Name);
        }
    }

结果：

4 Emp3
7 Emp6

Answer 2

使用 varbinary(892) 代替 hierarchyid。 EF 识别 varbinary 返回字节数组。 您可以将字节数组转换为 SqlHierarchyid 类型并使用 hyrarchy pod 函数。 使用此解决方法，您甚至可以在其他数据库中使用 hierarchyid 函数。 请参阅http://www.casavillar.com.br/blog 了解更多详细信息以及指向 nugget 和 github 的链接，您可以在其中找到包括 MySql 在内的示例