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Entity Relationship
中文 | English
Navigation properties are one of FreeSql's characteristic functions, which can be configured by agreement or customized configuration of the relationship between objects.
Navigation properties have five configuration relationships: OneToMany, ManyToOne, ManyToMany, OneToOne, and Parent.
With navigation properties, multi-table query is very convenient. Directly using navigation objects in lambda expressions can get the IDE's BUFF blessing.
- Naming convention,or not (need to specify Navigate attribute association);
- If there is no association relationship, you can specify the
Oncondition when querying,LeftJoin(a => a.Parent.Id == a.ParentId); - If there is an association relationship, just use the navigation object directly, and the
Oncondition will be automatically attached;
《What problems can navigation properties solve?》
//Navigation properties, OneToMany
[Navigate(nameof(song_tag.song_id))]
public virtual List<song_tag> Obj_song_tag { get; set; }
//Find the song_id property in song_tag and associate it with this ENTITY.PrimaryKey
//Navigation properties, ManyToOne/OneToOne
[Navigate(nameof(song_id))]
public virtual Song Obj_song { get; set; }
//Find the song_id property in THIS ENTITY and associate it with the Song.PrimaryKey
//Navigation properties, ManyToMany
[Navigate(ManyToMany = typeof(tag_song))]
public virtual List<tag> tags { get; set; }You can also use FluentApi to set the navigation relationship externally:
fsql.CodeFirst.ConfigEntity<YOUR_ENTITY>(a => a
.Navigate(b => b.roles, null, typeof(MANY_TO_MANY_MID_ENTITY))
.Navigate(b => b.users, "uid")
);Priority: Attribute> FluentApi
Note:
1、属性设置 Column(IsIgnore = true) 后，导航属性会失效
2、Navigate 设置的字符串是 类属性名，不是表 字段名！！！
How to detect whether a navigation property is configured to take effect:
var tbref = fsql.CodeFirst
.GetTableByEntity(typeof(T))
.GetTableRef("Children", true);Method signature:
GetTableRef(string propertyName, bool isThrow);
class User {
public int Id { get; set; } //Id、UserId、User_id
public UserExt UserExt { get; set; }
}
class UserExt {
public int id { get; set; } //Id、UserId、User_id、UserExtId、UserExt_id
public User User { get; set; }
}《How to add data in one-to-one mode?》
class Group {
public int Id { get; set; } //Id、GroupId、Group_id
}
class User {
public int Id { get; set; } //Id、UserId、User_id
public int AGroupId { get; set; }
public Group AGroup { get; set; }
public int BGroupId { get; set; }
public Group BGroup { get; set; }
}class Group {
public int Id { get; set; } //Id、GroupId、Group_id
public ICollection<User> AUsers { get; set; }
public ICollection<User> BUsers { get; set; }
}
class User {
public int Id { get; set; } //Id、UserId、User_id
public int AGroupId { get; set; }
public Group AGroup { get; set; }
public int BGroupId { get; set; }
public Group BGroup { get; set; }
}《How to add data in one-to-many mode?》
class Group {
public int Id { get; set; } //Id、GroupId、Group_id
public int ParentId { get; set; } //ParentId、Parent_id
public Group Parent { get; set; }
public ICollection<Group> Childs { get; set; }
}The parent-children relationship is similar to One-to-Many mode. You can also refer to this link:
《How to add data in one-to-many mode?》
class Song {
[Column(IsIdentity = true)]
public int Id { get; set; }
public string Title { get; set; }
public virtual ICollection<Tag> Tags { get; set; }
}
class Song_tag {
public int Song_id { get; set; }
public virtual Song Song { get; set; }
public int Tag_id { get; set; }
public virtual Tag Tag { get; set; }
}
class Tag {
[Column(IsIdentity = true)]
public int Id { get; set; }
public string Name { get; set; }
public int? Parent_id { get; set; }
public virtual Tag Parent { get; set; }
public virtual ICollection<Song> Songs { get; set; }
public virtual ICollection<Tag> Tags { get; set; }
}Song, Tag, Song_tag, these three entities use the four relationships: OneToMany, ManyToOne, Parent, and ManyToMany.