实体框架核心首先添加唯一约束代码

Question

我找不到为我的field属性添加唯一约束的方法

public class User
{
    [Required]
    public int Id { get; set; }

    [Required]
    // [Index("IX_FirstAndSecond", 2, IsUnique = true)] not supported by core
    public string Email { get; set; }

    [Required]
    public string Password { get; set; }
}

我在用

 "Microsoft.EntityFrameworkCore": "1.0.1",
 "Microsoft.EntityFrameworkCore.SqlServer": "1.0.1",
 "Microsoft.EntityFrameworkCore.SqlServer.Design": "1.0.1",
 "Microsoft.EntityFrameworkCore.Tools": "1.0.0-preview2-final",

Answer 1

在EF核心上,您无法使用数据注释创建索引.但您可以使用Fluent API执行此操作.

在你的内心像这样{Db}Context.cs:

protected override void OnModelCreating(ModelBuilder builder)
{
    builder.Entity<User>()
        .HasIndex(u => u.Email)
        .IsUnique();
}

...或者如果你在buildAction中使用了重载:

protected override void OnModelCreating(ModelBuilder builder)
{
    builder.Entity<User>(entity => {
        entity.HasIndex(e => e.Email).IsUnique();
    });
}

你可以在这里阅读更多相关信息:索引

Answer 2

此外,如果您想在多个列上创建唯一约束,您可以简单地执行此操作(遵循@ Sampath的链接)

class MyContext : DbContext
{
    public DbSet<Person> People { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>()
            .HasIndex(p => new { p.FirstName, p.LastName })
            .IsUnique(true);
    }
}

public class Person
{
    public int PersonId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

Answer 3

从 Entity Framework Core (EF Core) 5.0 开始，我们可以通过 Data Annotations 配置唯一索引。

它与例如 EF6 几乎没有什么不同，因为我们不能在属性本身上设置它，而是在类上设置它。

[Index(nameof(EmailAddress), IsUnique = true)]
public class User
{
    [Key]
    public Guid Id { get; set; }

    [Required]
    public string FullName { get; set; }

    [Required]
    public string EmailAddress { get; set; }
}

有关索引和数据注释的更多信息，请参阅：https : //docs.microsoft.com/en-us/ef/core/modeling/indexes?tabs= data-annotations

Answer 4

OP 询问是否可以将属性添加到实体类中作为唯一键。简而言之，这是可能的，但不是 EF Core 团队开箱即用的功能。如果您想使用属性将唯一键添加到 Entity Framework Core 实体类，您可以执行我在此处发布的操作

public class Company
{
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public Guid CompanyId { get; set; }

    [Required]
    [UniqueKey(groupId: "1", order: 0)]
    [StringLength(100, MinimumLength = 1)]
    public string CompanyName { get; set; }

    [Required]
    [UniqueKey(groupId: "1", order: 1)]
    [StringLength(100, MinimumLength = 1)]
    public string CompanyLocation { get; set; }
}

Answer 5

通过模型配置在 EF 核心中使用它

public class ApplicationCompanyConfiguration : IEntityTypeConfiguration<Company>
{
    public void Configure(EntityTypeBuilder<Company> builder)
    {
        builder.ToTable("Company"); 
        builder.HasIndex(p => p.Name).IsUnique();
    }
}

Answer 6

EF Core的解决方案

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Passport { get; set; }
}

public class ApplicationContext : DbContext
{
    public DbSet<User> Users { get; set; }
    public ApplicationContext()
    {
        Database.EnsureCreated();
    }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=efbasicsappdb;Trusted_Connection=True;");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>().HasAlternateKey(u => u.Passport);
        //or: modelBuilder.Entity<User>().HasAlternateKey(u => new { u.Passport, u.Name})
    }
}

DB表将如下所示:

CREATE TABLE [dbo].[Users] (
    [Id]       INT            IDENTITY (1, 1) NOT NULL,
    [Name]     NVARCHAR (MAX) NULL,
    [Passport] NVARCHAR (450) NOT NULL,
    CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ([Id] ASC),
    CONSTRAINT [AK_Users_Passport] UNIQUE NONCLUSTERED ([Passport] ASC)
);

参考EF核心文档

Answer 7

Ef 核心支持独特的配置。

protected override void OnModelCreating(ModelBuilder builder)
{
  builder.Entity<Account>()
    .HasIndex(account => account.Email)
      .IsUnique();
}

ef core 支持多个唯一键

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
  modelBuilder.Entity<Account>()
      .HasKey(account => new { account.Id, account.Email, account.RoleId });
}

不要忘记运行 ef core 命令来进行迁移和更新数据库

>> dotnet ef migrations add MigrationName -c YourDbContextName
>> dotnet ef database update -c YourDbContextName