EF code first Study Notes: Agreed Configuration

There are two methods to change the default configuration in EF. One is to use data annotations (in the namespace system. componentmodel. dataannotations;), directly acting on the attributes of the class; another is the fluent API, which overwrites the default configuration by adding the corresponding configuration class. Now we can use these two to compare and understand the agreed configuration in EF.

Primary Key: Key

Data Annotations: identifies a primary key using the key keyword

[Key]public int DestinationId { get; set; }

Fluent API:

public class BreakAwayContext : DbContext    {        public DbSet<Destination> Destinations { get; set; }        public DbSet<Lodging> Lodgings { get; set; }        protected override void OnModelCreating(DbModelBuilder modelBuilder)        {            //Fluent API            modelBuilder.Entity<Destination>().HasKey(d => d.DestinationId);            base.OnModelCreating(modelBuilder);        }    } 

Foreign key

Data Annotations:

        public int DestinationId { get; set; }        [ForeignKey("DestinationId")]        public Destination Destination { get; set; }

Note: If the specified column name exists, the destinationid must exist in the class.

Fluent API:

modelBuilder.Entity<Lodging>().HasRequired(p => p.Destination).WithMany(p=>p.Lodgings).HasForeignKey(p => p.DestinationId);

Length

Data Annotations: Set the length of fields in the database through stringlength (length), minlength (minimum length), and maxlength (maximum length.

        [MinLength(10),MaxLength(30)]        public string Name { get; set; }        [StringLength(30)]        public string Country { get; set; }

Fluent API: the minimum length is not set.

modelBuilder.Entity<Destination>().Property(p => p.Name).HasMaxLength(30);            modelBuilder.Entity<Destination>().Property(p => p.Country).HasMaxLength(30);

Not empty

Data Annotations: It is identified by required. You can also set whether to allow null strings and Display error messages.

[Required] Public String country {Get; set;} [required (errormessage = "Enter description")] Public String description {Get; set ;}

Fluent API:

modelBuilder.Entity<Destination>().Property(p => p.Country).IsRequired();

Data Type

Data Annotations: typename

// Map string to ntext. The default value is nvarchar (max) [column (typename = "ntext")] Public String owner {Get; set ;}

Fluent API:

modelBuilder.Entity<Lodging>().Property(p => p.Owner).HasColumnType("ntext");

Table Name

Data Annotations: Table

[Table("MyLodging")]    public class Lodging    {        public int LodgingId { get; set; }        public string Name { get; set; }        public string Owner { get; set; }            public decimal Price { get; set; }        public bool IsResort { get; set; }        public Destination Destination { get; set; }    } 

Fluent API:

modelBuilder.Entity<Lodging>().ToTable("MyLodging");

Column name

Data Annotations: Column

[Column("MyName")]public string Name { get; set; }

Fluent API:

modelBuilder.Entity<Lodging>().Property(p => p.Name).HasColumnName("MyName");

Self-Growth

If the primary key is of the int type, EF is set to increase by default. However, if it is of the guid type, the settings to be displayed are automatically increased.

Data Annotations: databasegenerated

  public class Person    {        [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]        public Guid SocialId { get; set; }        public string FirstName { get; set; }        public string LastName { get; set; }    }

Let's look at the data creation script and add one sentence.

ALTER TABLE [dbo].[People] ADD  DEFAULT (newid()) FOR [SocialId]

Fluent API:

modelBuilder.Entity<Person>().Property(p => p.SocialId).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

Ignore column ing

Some attributes in the class, especially the results obtained by calculating or merging columns, do not need to be recorded in the database, so we can configure it to prevent it from being generated in the database.

Data Annotations: notmapped

        [NotMapped]        public string Name        {            get             {                return FirstName + " " + LastName;            }        }

Fluent API: notmapped

modelBuilder.Entity<Person>().Ignore(p => p.Name);

Ignore table ing

For tables that do not need to be mapped to the database, we can also cancel the ing.

Data Annotations:

 [NotMapped]    public class Person    {        [Key]        public Guid SocialId { get; set; }        public string FirstName { get; set; }        public string LastName { get; set; }    }

Fluent API:

modelBuilder.Ignore<Person>();

Timestamp

The timestamp is only valid for attributes with the Data Type of byte [], and only one attribute set as the timestamp can be in a class.

Data Annotations: Timestamp

    1541178922    public Byte[] TimeStamp { get; set; }

Fluent API:

modelBuilder.Entity<Lodging>().Property(p => p.TimeStamp).IsRowVersion();

Complex types

Data Annotations: complextype

 [ComplexType]    public class Address    {        public string Country { get; set; }        public string City { get; set; }    }

Fluent API:

modelBuilder.ComplexType<Address>();

For more information about what a complex type is, see: http://www.cnblogs.com/Gyoung/archive/2013/01/17/2864747.html

 

EF code first Study Notes: Agreed Configuration