Data annotation Feature--foreignkey

A foreign key attribute that can be applied to the properties of a class. Code-first The default convention, the foreign key attribute assumes that the name of the foreign key property and the primary key attribute are matched.

Let's take a look at the following code:

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel.DataAnnotations;usingSystem.ComponentModel.DataAnnotations.Schema;usingSystem.Linq;usingSystem.Text;usingSystem.Threading.Tasks;namespaceef2{[Table ("Studentmaster", schema="Wahaha")]    Public classStudent {[Key] [Column (Order=5)]         Public intStudentKey1 {Get;Set; }        [Key] [Column (Order=6)]         Public intStudentKey2 {Get;Set; } [MaxLength ( -] [Concurrencycheck] [Required] [Column ("SName", order=1, typename="nvarchar")]         Public stringStudentname {Get;Set; } [Notmapped ()] Public int? Age {Get;Set; } public int StdId {get; set;} [ForeignKey ("StdId")] public Vsan standard {get; set; } }}

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel.DataAnnotations;usingSystem.Linq;usingSystem.Text;namespaceef2{ Public classStandard { [Key] public int StdId {get; set;}  Public stringStandardName {Get;Set; } }}

As you can see from the above figure, stdID is a foreign key in the student table and a primary key in the standard table.

Here is not the practice of using the class name +id, the foreign key is used.

The default is to use this:

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel.DataAnnotations;usingSystem.ComponentModel.DataAnnotations.Schema;usingSystem.Linq;usingSystem.Text;usingSystem.Threading.Tasks;namespaceef2{[Table ("Studentmaster", schema="Wahaha")]    Public classStudent {[Key] [Column (Order=5)]         Public intStudentKey1 {Get;Set; }        [Key] [Column (Order=6)]         Public intStudentKey2 {Get;Set; } [MaxLength ( -] [Concurrencycheck] [Required] [Column ("SName", order=1, typename="nvarchar")]         Public stringStudentname {Get;Set; } [Notmapped ()] Public int? Age {Get;Set; } public int Standardid {get; set;} Class name +id [ForeignKey ("Standardid")] public Vsan standard {get; set; } }}

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel.DataAnnotations;usingSystem.Linq;usingSystem.Text;namespaceef2{ Public classStandard { [Key] public int Standardid {get; set;} Class name +id Public stringStandardName {Get;Set; } }}

Look at the following:

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel.DataAnnotations;usingSystem.ComponentModel.DataAnnotations.Schema;usingSystem.Linq;usingSystem.Text;usingSystem.Threading.Tasks;namespaceef2{[Table ("Studentmaster", schema="Wahaha")]    Public classStudent {[Key] [Column (Order=5)]         Public intStudentKey1 {Get;Set; }        [Key] [Column (Order=6)]         Public intStudentKey2 {Get;Set; } [MaxLength ( -] [Concurrencycheck] [Required] [Column ("SName", order=1, typename="nvarchar")]         Public stringStudentname {Get;Set; } [Notmapped ()] Public int? Age {Get;Set; } public int Standardrefid {get; set;} [ForeignKey ("Standardrefid")] public Vsan standard {get; set; } }}

usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel.DataAnnotations;usingSystem.Linq;usingSystem.Text;namespaceef2{ Public classStandard { [Key] public int Standardid {get; set;}  Public stringStandardName {Get;Set; } }}

Look at the database:

This means that we can casually specify the name of the foreign key, hahaha haha ...

Data annotation Feature--foreignkey