[entity framework core] Entity Framework Core Property Configuration

https://www.learnentityframeworkcore.com/configuration/fluent-api/property-configuration

配置entity的属性是非常之常用的, 我们可以为属性进行长度等各方面的限制, 都可以使用 fluent api完成, 下面表格列出的是一些 api:

method	des
HasAnnotation	Provides a means to apply annotations via the Fluent API
HasColumnName	Specifies the name of the database column that the property should map to
HasColumnType	Specifies the data type of the database column that the property should map to
HasDefaultValue	Configures the default value of the database column that the property maps to
HasDefaultValueSql	Configures the default value expression for the database column that the property maps to
HasMaxLength	Specifies maximum length of data that can be stored for strings or binary data (arrays)
IsConcurrencyToken	Denotes that the property takes part in concurrency management
IsRequired	Configures the database column as not nullable
ValueGeneratedNever	Specifies that the database should not automatically generate values for the property
ValueGeneratedOnAdd	Specifies that values should only be generated automatically when new data is added
ValueGeneratedOnAddOrUpdate	Specifies that values should be generated automatically when data is added or updated

• example

    public class SampleContext : DbContext
    {
        public DbSet Books { get; set; }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity()
                .Property(b => b.Title).HasColumnName("Description");

            modelBuilder.Entity()
            .Property(b => b.Title).HasColumnType("varchar");

            modelBuilder.Entity()
            .Property(b => b.Title).HasMaxLength(150);

            modelBuilder.Entity()
            .Propery(p => p.IsActive).HasDefaultValue(true);

            modelBuilder.Entity()
            .Propery(p => p.DateCreated).HasDefaultValueSql("GetUtcDate()");

            modelBuilder.Entity()
            .Property(p => p.BookId).ValueGeneratedNever();
        }
    }
    public class Book
    {
        public int BookId { get; set; }
        public string Title { get; set; }
        public Author Author { get; set; }
        public bool IsActive { get; set; }
        public DateTime DateCreated { get; set; }
    }