ASP.NETCore使用EF创建模型(必需和可选属性、最大长度、并发标记、阴影属性)

namespace EFModeling.DataAnnotations.Required
{
    class MyContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }
    }
    public class Blog
    {
        public int BlogId { get; set; }
        //加上这个批注，这个值就必需写入
        [Required]
        public string Url { get; set; }
    }
}

namespace EFModeling.FluentAPI.Required
{
    class MyContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Blog>()
                .Property(b => b.Url)
                //这个方法表示必需写入
                .IsRequired();
        }
    }
    public class Blog
    {
        public int BlogId { get; set; }
        public string Url { get; set; }
    }
}

namespace EFModeling.DataAnnotations.MaxLength
{
    class MyContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }
    }
    public class Blog
    {
        public int BlogId { get; set; }
        //设置最大长度
        [MaxLength(500)]
        public string Url { get; set; }
    }
}

namespace EFModeling.FluentAPI.MaxLength
{
    class MyContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Blog>()
                .Property(b => b.Url)
                //设置最大长度
                .HasMaxLength(500);
        }
    }
    public class Blog
    {
        public int BlogId { get; set; }
        public string Url { get; set; }
    }
}

public class Person
{
　  public int PersonId { get; set; }
　   //并发标记
    [ConcurrencyCheck]
    public string LastName { get; set; }
    public string FirstName { get; set; }
}

class MyContext : DbContext
{
    public DbSet<Person> People { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>()
            .Property(p => p.LastName)
            //并发标记
            .IsConcurrencyToken();
    }
}
public class Person
{
    public int PersonId { get; set; }
    public string LastName { get; set; }
    public string FirstName { get; set; }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
    //设置时间戳
    1668328337
    public byte[] Timestamp { get; set; }
}

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .Property(p => p.Timestamp)
            //设置时间戳
            .IsRowVersion();
    }
}
public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
    public byte[] Timestamp { get; set; }
}

context.Entry(myBlog).Property("LastUpdated").CurrentValue = DateTime.Now;

var blogs = context.Blogs.OrderBy(b => EF.Property<DateTime>(b, "LastUpdated"));

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }
}
public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
    //阴影属性
    public List<Post> Posts { get; set; }
}
public class Post
{
    public int PostId { get; set; }
    public string Title { get; set; }
    public string Content { get; set; }
     //阴影属性
    public Blog Blog { get; set; }
}

class MyContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            //创建阴影属性
            .Property<DateTime>("LastUpdated");
    }
}
public class Blog
{
    public int BlogId { get; set; }
    public string Url { get; set; }
}