Code Frist 数据注解及Fluent API

表映射 [Table(string name, Properties:[Schema = string])

[Table("DataTest", Schema = "admin")]
 //注释：[Table(string name, Properties:[Schema = string])
 public class DataAnnotationsAttribute
 {
      [Key]
      [Column(Order = 1)]
      public int Id { get; set; }
}

列映射 [Column (string name, Properties:[Order = int],[TypeName = string])

  [Table("DataTest", Schema = "admin")]
        //注释：[Table(string name, Properties:[Schema = string])
        public class DataAnnotationsAttribute
        {
            [Key]
            [Column(Order = 1)]
            public int Id { get; set; }
 
            [Column(Order = 3, TypeName = "varchar(50)")]
            public string Name { get; set; }
 
            [Column("FullName", Order = 2, TypeName = "varchar(60)")]
            // [Column (string name, Properties:[Order = int],[TypeName = string])
            public string FullName { get; set; }
 
            // [ForeignKey] 参考 UserRole
            [DefaultValue(3)]
            public int DefaultValue { get; set; }
        }

Fluent api

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<DataAnnotationsAttribute>(eb =>
        {
            eb.Property(b => b.Name).HasColumnType("varchar(50)");
            eb.Property(b => b.FullName).HasColumnType("varchar(60)");
        });
    }

主键 [key]

数据注解方式：
[Key]
[Column(Order = 1)]
 public int Id { get; set; }
 
Fluent API
 
 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>() .HasKey(b => b.BlogId).HasName("PrimaryKey_BlogId");
    }

Fluent API

 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
         modelBuilder.Entity<Car>().HasKey(c => new { c.LicensePlate, c.State });
    }

计算列(列计算或拼接)：数据注解中无法实现，只能在Fluent API中实现

class MyContext : DbContext
{
    public DbSet<Person> People { get; set; }
 
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>()
            .Property(p => p.DisplayName)
            .HasComputedColumnSql("[LastName] + ', ' + [FirstName]");
    }
}
 
public class Person
{
    public int PersonId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string DisplayName { get; set; }
}

序列：数据注解中无法实现，只能在Fluent API中实现

class MyContext : DbContext
{
    public DbSet<Order> Orders { get; set; }
 
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.HasSequence<int>("OrderNumbers", schema: "shared")
            .StartsAt(1000)
            .IncrementsBy(5);
 
        modelBuilder.Entity<Order>()
            .Property(o => o.OrderNo)
            .HasDefaultValueSql("NEXT VALUE FOR shared.OrderNumbers");
    }
}
 
public class Order
{
    public int OrderId { get; set; }
    public int OrderNo { get; set; }
    public string Url { get; set; }
}

默认值：数据注解中无法实现（跟EF 不一样，即使提供，但没有效果），只能在Fluent API中实现

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
 
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(b => b.Rating)
            .HasDefaultValue(3);
    }
}
 
public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
    public int Rating { get; set; }
}

索引：数据注解中无法实现（跟EF 不一样，即使提供，但没有效果），只能在Fluent API中实现

protected override void OnModelCreating(ModelBuilder modelBuilder)
 {
    // 唯一索引
     modelBuilder.Entity<Blog>().HasIndex(b => b.Url).IsUnique();
    // 非唯一
     modelBuilder.Entity<Blog>().HasIndex(b => new { b.RegistrationNumber1, b.RegistrationNumber2 });
}

外键约束一对多：

// 实体
public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
 
    public int CurrentGradeId { get; set; }
    public Grade Grade { get; set; }
}
 
public class Grade
{
    public int GradeId { get; set; }
    public string GradeName { get; set; }
    public string Section { get; set; }
 
    public ICollection<Student> Students { get; set; }
}
// Fluent API
protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Student>()
            .HasOne<Grade>(s => s.Grade)
            .WithMany(g => g.Students)
            .HasForeignKey(s => s.CurrentGradeId);
    }
 
    public DbSet<Grade> Grades { get; set; }
    public DbSet<Student> Students { get; set; }

一对一：

// 实体
public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
       
    public StudentAddress Address { get; set; }
}
 
public class StudentAddress
{
    public int StudentAddressId { get; set; }
    public string Address { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Country { get; set; }
 
    public int AddressOfStudentId { get; set; }
    public Student Student { get; set; }
}
//Fluent API
protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Student>()
            .HasOne<StudentAddress>(s => s.Address)
            .WithOne(ad => ad.Student)
            .HasForeignKey<StudentAddress>(ad => ad.AddressOfStudentId);
    }
 
    public DbSet<Student> Students { get; set; }
    public DbSet<StudentAddress> StudentAddresses { get; set; }

多对多：

// 实体
public class StudentCourse
{
    public int StudentId { get; set; }
    public Student Student { get; set; }
 
    public int CourseId { get; set; }
    public Course Course { get; set; }
}
public class Student
{
    public int StudentId { get; set; }
    public string Name { get; set; }
 
    public IList<StudentCourse> StudentCourses { get; set; }
}
 
public class Course
{
    public int CourseId { get; set; }
    public string CourseName { get; set; }
    public string Description { get; set; }
 
    public IList<StudentCourse> StudentCourses { get; set; }
}
// Fluent API
 
modelBuilder.Entity<StudentCourse>().HasKey(sc => new { sc.SId, sc.CId });
 
modelBuilder.Entity<StudentCourse>()
    .HasOne<Student>(sc => sc.Student)
    .WithMany(s => s.StudentCourses)
    .HasForeignKey(sc => sc.SId);
 
 
modelBuilder.Entity<StudentCourse>()
    .HasOne<Course>(sc => sc.Course)
    .WithMany(s => s.StudentCourses)
    .HasForeignKey(sc => sc.CId);

排除实体和属性--NotMapped

// 实体
排除entity
public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
 
    public BlogMetadata Metadata { get; set; }
}
 
[NotMapped]
public class BlogMetadata
{
    public DateTime LoadedFromDatabase { get; set; }
}
排除属性
public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
 
    [NotMapped]
    public DateTime LoadedFromDatabase { get; set; }
}
//Fluent API
 排除entity
 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Ignore<BlogMetadata>();
    }
 排除属性
 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Ignore(b => b.LoadedFromDatabase);
    }

最大长度--MaxLength （Fluent API 中没有MinLength）

//实体
public class Blog
{
    public int BlogId { get; set; }
    [MaxLength(500)]
    public string Url { get; set; }
}
 
//Fluent API
 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(b => b.Url)
            .HasMaxLength(500);
    }

防并发：Timestamp 与ConcurrencyCheck

//实体
public class Person
{
    public int PersonId { get; set; }
 
    [ConcurrencyCheck]
    public string LastName { get; set; }
 
    //10 .Timestamp 时间戳必须是byte[]类型的,防止并发，EF 的并发都是乐观的。例如同时改一条数据，别人在你之前提交
    [Timestamp]
    public byte[] Timestamp { get; set; }
}
//Fluent API
 
protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(p => p.Timestamp)
            .IsRowVersion();
     modelBuilder.Entity<Blog>().Property(b => b.Timestamp).IsRowVersion();
    }

值转换

和Data Seeding 一起举例在进行数据库迁移时，EF会往数据库中插入一些数据

Data Seeding 这个是用来初始化数据用。

// 值类型转换
public class Blog
{
    public int BlogId { get; set; }
     public string Url { get; set; }
    public EquineBeast Mount { get; set; }
}
 
public enum EquineBeast
{
    Donkey,
    Mule,
    Horse,
    Unicorn
}
// fluent api 
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder
        .Entity<Rider>()
        .Property(e => e.Mount)
        .HasConversion(
            v => v.ToString(),
            v => (EquineBeast)Enum.Parse(typeof(EquineBeast), v));
    // DATA SEEDING
    modelBuilder.Entity<Blog>().HasData(new Blog { BlogId = 1, Url = "http://sample.com" });
 
}