EntityFramework Core personal memo

7 minute read

I put it in text on my desktop, but I thought I’d lose it, so make a note.

  • Please do not refer to
⓪ DB Maigure

  • First time
    Enable-Migrations

  • Create update file
    Add-Migration Post Name

  • Run
    Update-Database -Verbose

Entity Framework Core annotation

(1) [NotMapped]: Model property that is not added to the DB
② Primary key

For single unit: [Key]
modelBuilder.Entity (). HasKey (c => c. key name); Composite key: modelBuilder.Entity (). HasKey (c => new {c. key name 1, c. key name 2); 　　　

③ Automatic data generation

[DatabaseGenerated(DatabaseGeneratedOption.None)]　
Not automatically generated (useful if you want to set the primary key etc. as you like?)
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]　
Automatically allocated when a record is added
[DatabaseGenerated(DatabaseGeneratedOption.Computed)]　
Automatically allocated at the time of additional update

④ Not Null constraint

　[Required]

⑤ Maximum length

　[MaxLength(500)]

⑥ Optimistic exclusive control

DbUpdateConcurrencyException occurs
[Timestamp]: The line where the time stamp is saved when the line is updated and added.
Exclude check target → DbUpdateConcurrencyException occurs

⑦ Shadow property

It’s not defined in the model, but it can be used as a property of the model! What is that?
modelBuilder.Entity (). Property ("shadow property name");

How to Use
context.Entry (variable containing the model) .Property (“shadow property name”). CurrentValue = DateTime.Now;
var XXXX = context.XXXX.OrderBy (b => EF.Property (b, "shadow property name")); 　 ~~ I don't know how to use it ...? ~~

⑧ Relationship

　https://docs.microsoft.com/ja-jp/ef/core/modeling/relationships
　
A. Fully defined relationship

sample.cs


	public class Blog
	{
	    public int BlogId { get; set; }
	    public string Url { get; set; }

	    public List<Post> Posts { get; set; }
	}

	public class Post
	{
	    public int PostId { get; set; }
	    public string Title { get; set; }
	    public string Content { get; set; }

	    public int BlogId { get; set; }
	    public Blog Blog { get; set; }
	}

I. Foreign key property

sample.cs


	public class Blog
	{
	    public int BlogId { get; set; }
	    public string Url { get; set; }

	    public List<Post> Posts { get; set; }
	}

	public class Post
	{
	    public int PostId { get; set; }
	    public string Title { get; set; }
	    public string Content { get; set; }

	    public Blog Blog { get; set; }
	}

C. Single navigation property

sample.cs


	public class Blog
	{
	    public int BlogId { get; set; }
	    public string Url { get; set; }

	    public List<Post> Posts { get; set; }
	}

	public class Post
	{
	    public int PostId { get; set; }
	    public string Title { get; set; }
	    public string Content { get; set; }
	}

D. Data annotation
(1) When the name of the foreign key does not depend on the naming such as a fully defined relationship
[Foreign Key (“Foreign Key Name”)]

sample.cs


		public class Blog
		{
		    public int BlogId { get; set; }
		    public string Url { get; set; }

		    public List<Post> Posts { get; set; }
		}

		public class Post
		{
		    public int PostId { get; set; }
		    public string Title { get; set; }
		    public string Content { get; set; }

		    public int BlogForeignKey { get; set; }

		    [ForeignKey("BlogForeignKey")]
		    public Blog Blog { get; set; }
		}

(2) When two links are set from one model to the same model
[InverseProperty (“property name of linked model”)]

sample.cs


		public class Post
		{
		    public int PostId { get; set; }
		    public string Title { get; set; }
		    public string Content { get; set; }

		    public int AuthorUserId { get; set; }
		    public User Author { get; set; }

		    public int ContributorUserId { get; set; }
		    public User Contributor { get; set; }
		}

		public class User
		{
		    public string UserId { get; set; }
		    public string FirstName { get; set; }
		    public string LastName { get; set; }

		    [InverseProperty("Author")]
		    public List<Post> AuthoredPosts { get; set; }

		    [InverseProperty("Contributor")]
		    public List<Post> ContributedToPosts { get; set; }
		}

E. Composite foreign key (do you have to use Fluent?)
modelBuilder.Entity () .HasOne (model name for s => s.1) .WithMany (property name for c => c.1) .HasForeignKey (s => new {s. Many property names, s. Many property names});

F. Many-to-many

sample.cs


	class MyContext : DbContext
	{
	    public DbSet<Post> Posts { get; set; }
	    public DbSet<Tag> Tags { get; set; }

	    protected override void OnModelCreating(ModelBuilder modelBuilder)
	    {
	        modelBuilder.Entity<PostTag>()
	            .HasKey(t => new { t.PostId, t.TagId });

	        modelBuilder.Entity<PostTag>()
	            .HasOne(pt => pt.Post)
	            .WithMany(p => p.PostTags)
	            .HasForeignKey(pt => pt.PostId);

	        modelBuilder.Entity<PostTag>()
	            .HasOne(pt => pt.Tag)
	            .WithMany(t => t.PostTags)
	            .HasForeignKey(pt => pt.TagId);
	    }
	}

	public class Post
	{
	    public int PostId { get; set; }
	    public string Title { get; set; }
	    public string Content { get; set; }

	    public List<PostTag> PostTags { get; set; }
	}

	public class Tag
	{
	    public string TagId { get; set; }

	    public List<PostTag> PostTags { get; set; }
	}

	public class PostTag
	{
	    public int PostId { get; set; }
	    public Post Post { get; set; }

	    public string TagId { get; set; }
	    public Tag Tag { get; set; }
	}

⑨INDEX
modelBuilder.Entity (). HasIndex (b => b. property name to put Index); If you want to be unique. IsUnique () Multiple is possible. HasIndex (p => new {p. property name 1, p. property name 2});

⑩ Automatic property backing field

When expanding from DB, it is written directly to the backing field without using an accessor (it seems)

sample.cs


public class Blog
{
    private string _url; //← The naming convention for this is_<camel-cased property name>Or m_<camel-cased property name>

    public int BlogId { get; set; }

    public string Url
    {
        get { return _url; }
        set { _url = value; }
    }
}
⑪ Value conversion

It is saved under the name of Enum in the example. What is the usage? ??

sample.cs


	    public class Rider
		{
		   public int Id { get; set; }
		   public EquineBeast Mount { get; set; }
		}

		public enum EquineBeast
		{
		   Donkey,
		   Mule,
		   Horse,
		   Unicorn
		}
	protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder
        .Entity<Rider>()
        .Property(e => e.Mount)
        .HasConversion(
            v => v.ToString(),
            v => (EquineBeast)Enum.Parse(typeof(EquineBeast), v));
}
⑫ Owned entity type

Can be used like a nest. One real table

sample.cs


	[Owned]
	public class StreetAddress
	{
	    public string Street { get; set; }
	    public string City { get; set; }
	}
	public class Order
	{
	    public int Id { get; set; }
	    public StreetAddress ShippingAddress { get; set; }
	}

OnModelCreating

sample.cs


            #region OwnsOne
            modelBuilder.Entity<Order>().OwnsOne(p => p.ShippingAddress);
            #endregion

            #region OwnsOneString
            modelBuilder.Entity<Order>().OwnsOne(typeof(StreetAddress), "ShippingAddress");
            #endregion

            #region ColumnNames
            modelBuilder.Entity<Order>().OwnsOne(
                o => o.ShippingAddress,
                sa =>
                {
                    sa.Property(p => p.Street).HasColumnName("ShipsToStreet");
                    sa.Property(p => p.City).HasColumnName("ShipsToCity");
                });
            #endregion

After that, restrictions on the DB

⑭ Table mapping

sample.cs


  [Table("blogs")]
  [Table("blogs", Schema = "blogging")] //Schema settings
⑮ nvarchar (max) column mapping

sample.cs


 [Column("blog_id")]
⑯ Data type

　 [Column(TypeName = “varchar(200)”)]　decimal(5, 2)　nvarchar(max)　DateTime
The types that can be used differ depending on the DB

⑰ Primary key

　　　　[Key]
If you want to name

sample.cs


        modelBuilder.Entity<Blog>()
            .HasKey(b => b.BlogId)
            .HasName("PrimaryKey_BlogId");
⑱ Default schema

sample.cs


   modelBuilder.HasDefaultSchema("blogging");
⑲ Calculation column

A calculation column cannot be created in the DB, but how can it be used?

sample.cs


	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; }
	}
⑳ Sequence
  • Not associated with a specific table

sample.cs


   modelBuilder.HasSequence<int>("OrderNumbers");
㉑ Default value Initial value

sample.cs


	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; }
	}
  • You can also use SQL fragments.

sample.cs


.HasDefaultValueSql("getdate()");
㉒ Index

sample.cs


        modelBuilder.Entity<Blog>()
            .HasIndex(b => b.Url)
            .HasName("Index_Url");
㉓ Filter

sample.cs


        modelBuilder.Entity<Blog>()
            .HasIndex(b => b.Url)
            .HasFilter("[Url] IS NOT NULL");
㉔ Foreign key constraint

sample.cs


	class MyContext : DbContext
	{
	    public DbSet<Blog> Blogs { get; set; }
	    public DbSet<Post> Posts { get; set; }

	    protected override void OnModelCreating(ModelBuilder modelBuilder)
	    {
	        modelBuilder.Entity<Post>()
	            .HasOne(p => p.Blog)
	            .WithMany(b => b.Posts)
	            .HasForeignKey(p => p.BlogId)
	            .HasConstraintName("ForeignKey_Post_Blog");
	    }
	}

	public class Blog
	{
	    public int BlogId { get; set; }
	    public string Url { get; set; }

	    public List<Post> Posts { get; set; }
	}

	public class Post
	{
	    public int PostId { get; set; }
	    public string Title { get; set; }
	    public string Content { get; set; }

	    public int BlogId { get; set; }
	    public Blog Blog { get; set; }
	}

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