标签:stat close arch ota generated cli 意图 hang tin
1、EF多实体对应单表
适用场景:单数据库表,表数据有较长用字段,有不常用或者大数据字段。
2、建表语句
CREATE TABLE [Chapter2].[Photograph]( [PhotoId] [int] IDENTITY(1,1) primary key NOT NULL, [Title] [varchar](50) NOT NULL, [ThumbnailBits] [image] NOT NULL, [HighResolutionBits] [image] NOT NULL )
3、新建控制程序,添加EntityFramework 引用。
4、创建两个实体实体,实体由同一个表不同字段组成。
public class PictureContext : DbContext { public DbSet<Photograph> Photographs { get; set; } public DbSet<PhotographFullImage> PhotographFullImage { get; set; } public PictureContext() : base("EFRecipesEntities") { } protected override void OnModelCreating(DbModelBuilder modelBuilder) { base.OnModelCreating(modelBuilder); modelBuilder.Entity<Photograph>() .HasRequired(p => p.PhotographFullImage) .WithRequiredPrincipal(p => p.Photograph); modelBuilder.Entity<Photograph>().ToTable("Photograph", "Chapter2"); modelBuilder.Entity<PhotographFullImage>().ToTable("Photograph", "Chapter2"); } } public class Photograph { [Key] [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int PhotoId { get; set; } public string Title { get; set; } public byte[] ThumbnailBits { get; set; } [ForeignKey("PhotoId")] public virtual PhotographFullImage PhotographFullImage { get; set; } } public class PhotographFullImage { [Key] public int PhotoId { get; set; } public byte[] HighResolutionBits { get; set; } [ForeignKey("PhotoId")] public virtual Photograph Photograph { get; set; } }
注意图中指定Photograph实体需要(HasRequired) PhotographFullImage实体,并通过WithRequiredPrincipal,指定主键由Photograph负责。
5、修改Main程序如下:
static void Main(string[] args) { byte[] thumbBits = new byte[100]; byte[] fullBits = new byte[2000]; using (var context = new PictureContext()) { var photo = new Photograph { Title = "My Dog", ThumbnailBits = thumbBits }; var fullImage = new PhotographFullImage { HighResolutionBits = fullBits }; photo.PhotographFullImage = fullImage; context.Photographs.Add(photo); context.SaveChanges(); } using (var context = new PictureContext()) { foreach (var photo in context.Photographs) { Console.WriteLine("Photo: {0}, ThumbnailSize {1} bytes", photo.Title, photo.ThumbnailBits.Length); // explicitly load the "expensive" entity, context.Entry(photo).Reference(p => p.PhotographFullImage).Load(); Console.WriteLine("Full Image Size: {0} bytes", photo.PhotographFullImage.HighResolutionBits.Length); } } Console.ReadKey(); }
标签:stat close arch ota generated cli 意图 hang tin
原文地址:https://www.cnblogs.com/bro-ma/p/10703890.html