根据类型继承手动设置实体框架的表答案

【问题标题】：Manually set up Entity Framework's Table per type inheritance根据类型继承手动设置实体框架的表
【发布时间】：2015-02-05 18:25:35
【问题描述】：

我有一些现有的表和模型是手动设置的，它们只是依赖于实体的隐式关联。我没有 edmx 文件或设计器或映射向导。

我想按每个类型的表建立一个继承关联，这样我就可以有一个由一个表表示的基类，然后有其他表表示继承类的附加字段。有没有办法只用模型和表格来做到这一点。默认情况下，Entity 尝试将结构作为每个层次结构的表来访问，并引发错误，因为继承的类成员不存在于表示基类的表中。

例如：

public class FormBase
{
    [Key]
    public long Id { get; set; }

    public int UserId { get; set; }

    public string FormType { get; set; }

    public int Status { get; set; }

    public int? Hidden { get; set; }

    public DateTime DateSubmitted { get; set; }

    public DateTime DateFinalized { get; set; }
}

CREATE TABLE [dbo].[FormBases] (
    [Id]            BIGINT         IDENTITY (1, 1) NOT NULL,
    [UserId]        INT            NOT NULL,
    [FormType]      NVARCHAR (100) NOT NULL,
    [Status]        INT            DEFAULT ((0)) NOT NULL,
    [Hidden]        INT            DEFAULT ((0)) NOT NULL,
    [DateSubmitted] DATETIME2 (7)  NULL,
    [DateFinalized] DATETIME2 (7)  NULL,
    PRIMARY KEY CLUSTERED ([Id] ASC)
);

public class CheckRequestModel : FormBase
{
    [Display(Name="Requester Name")]
    public string RequestorName { get; set; }
    [Display(Name="Phone Number")]
    public string PhoneNumber { get; set; }
    [Display(Name="E-mail")]
    public string Email { get; set; }
    [Display(Name="Name")]
    public string PayToName { get; set; }
    [Display(Name="Address")]
    public string PayToAddress { get; set; }
    [Display(Name="City")]
    public string PayToCity { get; set; }
    [Display(Name="State")]
    public string PayToState { get; set; }
    [Display(Name="Zip")]
    public int PayToZip { get; set; }

    public bool ReceiptAttached { get; set; }

    [Display(Name="Receipt")]
    public Attachment Receipt { get; set; }

    [ForeignKey("Receipt")]
    public long? ReceiptId { get; set; }

    public bool InvoiceAttached { get; set; }
    [Display(Name="Invoice")]
    public Attachment Invoice { get; set; }

    [ForeignKey("Invoice")]
    public long? InvoiceId { get; set; }

    [Display(Name="Date")]
    public DateTime? Date { get; set; }

    [Display(Name="Total Amount")]
    [DataType(DataType.Currency)]
    public Decimal? TotalAmount { get; set; }

    [Display(Name="Purchase Requisition Type")]
    public string PurchaseRequisitionType { get; set; }

    [Display(Name="Purpose Description")]
    public string PurposeDescription { get; set; }

    [Display(Name="Allocations")]
    public List<AllocationInformation> Allocations { get; set; }

    [Display(Name="Allocation Total")]
    [DataType(DataType.Currency)]
    public Decimal? AllocationTotal { get; set; }
}


CREATE TABLE [dbo].[CheckRequestModels] (
    [Id]                      BIGINT         IDENTITY (1, 1) NOT NULL,
    [UserId]                  INT            NOT NULL,
    [Status]                  INT            NOT NULL,
    [DateSubmitted]           DATETIME2 (7)  NULL,
    [DateFinalized]           DATETIME2 (7)  NULL,
    [FormType]                NVARCHAR (MAX) DEFAULT ('CheckRequest') NULL,
    [Hidden]                  INT            NULL,
    [RequestorName]           NVARCHAR (MAX) NOT NULL,
    [PhoneNumber]             NVARCHAR (MAX) NOT NULL,
    [Email]                   NVARCHAR (MAX) NOT NULL,
    [PayToName]               NVARCHAR (MAX) NOT NULL,
    [PayToAddress]            NVARCHAR (MAX) NOT NULL,
    [PayToCity]               NVARCHAR (MAX) NOT NULL,
    [PayToState]              NVARCHAR (MAX) NOT NULL,
    [PayToZip]                INT            NOT NULL,
    [ReceiptAttached]         BIT            DEFAULT ((0)) NOT NULL,
    [InvoiceAttached]         BIT            DEFAULT ((0)) NOT NULL,
    [Date]                    DATETIME2 (7)  NOT NULL,
    [TotalAmount]             DECIMAL (18)   NOT NULL,
    [PurchaseRequisitionType] NVARCHAR (MAX) NOT NULL,
    [PurposeDescription]      NVARCHAR (MAX) NOT NULL,
    [AllocationTotal]         DECIMAL (18)   NOT NULL,
    [InvoiceId]               INT            NULL,
    [ReceiptId]               INT            NULL,
    PRIMARY KEY CLUSTERED ([Id] ASC)
);

目前我在继承表中仍然有来自基类的字段。如果我删除这些实体会弄清楚我想要什么还是我需要做其他事情？

【问题讨论】：

我在weblogs.asp.net/ricardoperes/…有一个教程，看看有没有帮助。
好的，我只需要用[Table("Name")]注解来注解吗？
好的，我试过了，我认为它几乎可以工作，但它一直在寻找一个鉴别器列，好像它仍在使用层次结构。

标签： c# asp.net-mvc entity-framework inheritance table-per-type

【解决方案1】：

将DbSet指定为抽象类型的集合，然后将派生类型映射到另一个表：

public class MyDbContext : DbContext
{
    public DbSet<FormBase> Forms { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<CheckRequestModel>().Map(r => {
            r.ToTable("CheckRequests");
        });
    }
}

这样就可以了。

【讨论】：