EF CodeFirst系列(7)--- FluentApi配置单个实体

  我们已经知道了在OnModelCreating()方法中可以通过FluentApi对所有的实体类进行配置,然而当实体类很多时,我们把所有的配置都放在OnModelCreating()方法中很难维护。EF6允许我们给每一个实体添加一个单独的配置类,通过这个配置类来对相应的实体进行配置

  以配置Student实体类为例,我们在OnModelCreating()方法中配置Student实体,代码如下:

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

    public DbSet<Student> Students { get; set; }
        
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
            modelBuilder.Entity<Student>().ToTable("StudentInfo");
                
            modelBuilder.Entity<Student>().HasKey<int>(s => s.StudentKey);
                
            modelBuilder.Entity<Student>()
                    .Property(p => p.DateOfBirth)
                    .HasColumnName("Birthday")
                    .HasColumnOrder(3)
                    .HasColumnType("datetime2");

            modelBuilder.Entity<Student>()
                    .Property(p => p.StudentName)
                    .HasMaxLength(50);
                        
                modelBuilder.Entity<Student>()
                    .Property(p => p.StudentName)
                    .IsConcurrencyToken();
                
            modelBuilder.Entity<Student>()
                .HasMany<Course>(s => s.Courses)
                .WithMany(c => c.Students)
                .Map(cs =>
                        {
                            cs.MapLeftKey("StudentId");
                            cs.MapRightKey("CourseId");
                            cs.ToTable("StudentCourse");
                        });
    }
}

  我们可以将每个实体类的配置放在一个对应的的配置类,(如Studnet的实体配置在StudentEntityConfiguratinos配置类中),如果程序中有很多实体类,采用单独配置的方式可以很好的提高配置的可维护性和可读性。

步骤如下:

步骤①:创建一个StudentEntityConfiguratinos类,这个类继承 EntityTypeConfiguration<TEntity> ,代码如下:

public class StudentEntityConfiguration: EntityTypeConfiguration<Student>
{
    public StudentEntityConfiguration()
    {
            this.ToTable("StudentInfo");
                
            this.HasKey<int>(s => s.StudentKey);
                
            this.Property(p => p.DateOfBirth)
                    .HasColumnName("DoB")
                    .HasColumnOrder(3)
                    .HasColumnType("datetime2");

            this.Property(p => p.StudentName)
                    .HasMaxLength(50);
                        
            this.Property(p => p.StudentName)
                    .IsConcurrencyToken();
                
            this.HasMany<Course>(s => s.Courses)
                .WithMany(c => c.Students)
                .Map(cs =>
                        {
                            cs.MapLeftKey("StudentId");
                            cs.MapRightKey("CourseId");
                            cs.ToTable("StudentCourse");
                        });
    }
}

步骤②: 在OnModelCreating()方法中使用上边的配置类

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

    public DbSet<Student> Students { get; set; }
        
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // 添加Student实体的配置
        modelBuilder.Configurations.Add(new StudentEntityConfiguration());
    }
}

 

posted @ 2018-09-25 12:43  捞月亮的猴子  阅读(...)  评论(... 编辑 收藏