EF Code-First 学习之旅 Fluent API

Mappings	To Database
Model-wide Mapping	Set default Schema Set Custom Convetions
Entity Mapping	To Single or Multiple Tables and Schema To Complex type Inheritance Hierarchies
Property Mapping	To Column, Column Name, Column Type, Nullable or Not Null Column, Column size, Columns Order To Concurrency column To Foreign key column To configure relationships

public class SchoolContext: DbContext 
{
    public SchoolDBContext(): base() 
    {
    }

    public DbSet<Student> Students { get; set; }
    public DbSet<Standard> Standards { get; set; }
        
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Configure domain classes using modelBuilder here

        base.OnModelCreating(modelBuilder);
    }
}

在OnModelCreating方法中配置Fluent API

Code First配置优先顺序为：Fluent API > DataAnnotations > default conventions

EntityTypeConfiguration

EntityTypeConfiguration是一个重要的类，

Method Name	Return Type	Description
HasKey<TKey>	EntityTypeConfiguration	为实体类配置主键
HasMany<TTargetEntity>	ManyNavigationPropertyConfiguration	配置多对多的关系
HasOptional<TTargetEntity>	OptionalNavigationPropertyConfiguration	配置从这个实体中可选的关系，这个实体的实例可以没有和关系就保存到数据库中，数据库中的外键可为nullable
HasRequired<TTargetEntity>	RequiredNavigationPropertyConfiguration	配置从这个实体中必须的关系，实体的实例如果没有指定关系不能保存在数据库中，数据库外键为non-nullable
Ignore<TProperty>	Void	排除实体的属性不映射到数据库中
Map	EntityTypeConfiguration	允许与此实体类型映射到数据库架构的高级配置有关。
Property<T>	StructuralTypeConfiguration	配置在该类型上定义的结构属性
ToTable	Void	配置此实体类型映射到的表名。

Entity Mappings

public class Student
{
    public Student()
    { 
        
    }
    public int StudentID { get; set; }
    public string StudentName { get; set; }
    public DateTime? DateOfBirth { get; set; }
    public byte[]  Photo { get; set; }
    public decimal Height { get; set; }
    public float Weight { get; set; }
        
    public Standard Standard { get; set; }
}
    
public class Standard
{
    public Standard()
    { 
        
    }
    public int StandardId { get; set; }
    public string StandardName { get; set; }
    
    public ICollection<Student> Students { get; set; }
   
    }

Configure Default Schema

public class SchoolContext: DbContext 
{
    public SchoolDBContext(): base() 
    {
    }

    public DbSet<Student> Students { get; set; }
    public DbSet<Standard> Standards { get; set; }
        
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Configure default schema
        modelBuilder.HasDefaultSchema("Admin");
    }
}

 配置实体映射到表

namespace CodeFirst_FluentAPI_Tutorials
{
        
    public class SchoolContext: DbContext 
    {
        public SchoolDBContext(): base() 
        {
        }

        public DbSet<Student> Students { get; set; }
        public DbSet<Standard> Standards { get; set; }
        
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
                //Configure default schema
            modelBuilder.HasDefaultSchema("Admin");
                    
            //Map entity to table
            modelBuilder.Entity<Student>().ToTable("StudentInfo");
            modelBuilder.Entity<Standard>().ToTable("StandardInfo","dbo");

        }
    }
}

 

配置实体到多个表中

namespace CodeFirst_FluentAPI_Tutorials
{
        
    public class SchoolContext: DbContext 
    {
        public SchoolDBContext(): base() 
        {
        }

        public DbSet<Student> Students { get; set; }
        public DbSet<Standard> Standards { get; set; }
        
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Student>().Map(m =>
            {
                m.Properties(p => new { p.StudentId, p.StudentName});
                m.ToTable("StudentInfo");

            }).Map(m => {
                m.Properties(p => new { p.StudentId, p.Height, p.Weight, p.Photo, p.DateOfBirth});
                m.ToTable("StudentInfoDetail");

            });

            modelBuilder.Entity<Standard>().ToTable("StandardInfo");

        }
    }
}

 

Property Mappings 

public class SchoolContext: DbContext 
{
    public SchoolDBContext(): base() 
    {
    }

    public DbSet<Student> Students { get; set; }
    public DbSet<Standard> Standards { get; set; }
        
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Configure primary key
        modelBuilder.Entity<Student>().HasKey<int>(s => s.StudentKey);
        modelBuilder.Entity<Standard>().HasKey<int>(s => s.StandardKey);

        //Configure composite primary key
        modelBuilder.Entity<Student>().HasKey<int>(s => new { s.StudentKey, s.StudentName }); 
    }
}

public class SchoolContext: DbContext 
{
    public SchoolDBContext(): base() 
    {
    }

    public DbSet<Student> Students { get; set; }
    public DbSet<Standard> Standards { get; set; }
        
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //Configure Column
        modelBuilder.Entity<Student>()
                    .Property(p => p.DateOfBirth)
                    .HasColumnName("DoB")
                    .HasColumnOrder(3)
                    .HasColumnType("datetime2");
    }
}

 

配置nullable和non-nullable

namespace CodeFirst_FluentAPI_Tutorials
{
        
    public class SchoolContext: DbContext 
    {
        public SchoolDBContext(): base() 
        {
        }

        public DbSet<Student> Students { get; set; }
        public DbSet<Standard> Standards { get; set; }
        
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
                //Configure Null Column
            modelBuilder.Entity<Student>()
                    .Property(p => p.Heigth)
                    .IsOptional();
                        
                //Configure NotNull Column
                modelBuilder.Entity<Student>()
                    .Property(p => p.Weight)
                    .IsRequired();
        }
    }
}

配置列的长度

namespace CodeFirst_FluentAPI_Tutorials
{
        
    public class SchoolContext: DbContext 
    {
        public SchoolDBContext(): base() 
        {
        }

        public DbSet<Student> Students { get; set; }
        public DbSet<Standard> Standards { get; set; }
        
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            //Set StudentName column size to 50
            modelBuilder.Entity<Student>()
                    .Property(p => p.StudentName)
                    .HasMaxLength(50);
                        
            //Set StudentName column size to 50 and change datatype to nchar 
            //IsFixedLength() change datatype from nvarchar to nchar
            modelBuilder.Entity<Student>()
                    .Property(p => p.StudentName)
                    .HasMaxLength(50).IsFixedLength();
                        
            //Set size decimal(2,2)
                modelBuilder.Entity<Student>()
                    .Property(p => p.Height)
                    .HasPrecision(2, 2);
        }
    }
}

配置并发列

namespace CodeFirst_FluentAPI_Tutorials
{
        
    public class SchoolContext: DbContext 
    {
        public SchoolDBContext(): base() 
        {
        }

        public DbSet<Student> Students { get; set; }
        public DbSet<Standard> Standards { get; set; }
        
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            //Set StudentName as concurrency column
            modelBuilder.Entity<Student>()
                    .Property(p => p.StudentName)
                    .IsConcurrencyToken();
        }
    }
}

也可以用IsRowVersion()来配置byte[]数组