Entity Framework Code First （四）Fluent API - 配置属性/类型

　　上篇博文说过当我们定义的类不能遵循约定（Conventions）的时候，Code First 提供了两种方式来配置你的类：DataAnnotations 和 Fluent API, 本文将关注 Fluent API. 

　　一般来说我们访问 Fluent API 是通过重写继承自 DbContext 的类中方法 OnModelCreating. 为了便于例示，我们先创建一个继承自 DbContext 的类，以及其它的一些类以便使用

public class SchoolEntities : DbContext
    {
        public DbSet<Course> Courses { get; set; }
        public DbSet<Department> Departments { get; set; }
        public DbSet<Instructor> Instructors { get; set; }
        public DbSet<OfficeAssignment> OfficeAssignments { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // Configure Code First to ignore PluralizingTableName convention
            // If you keep this convention then the generated tables will have pluralized names.
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
        }
    }

    public class Department
    {
        public Department()
        {
            this.Courses = new HashSet<Course>();
        }
        // Primary key
        public int DepartmentID { get; set; }
        public string Name { get; set; }
        public decimal Budget { get; set; }
        public System.DateTime StartDate { get; set; }
        public int? Administrator { get; set; }

        // Navigation property
        public virtual ICollection<Course> Courses { get; private set; }
    }

    public class Course
    {
        public Course()
        {
            this.Instructors = new HashSet<Instructor>();
        }
        // Primary key
        public int CourseID { get; set; }

        public string Title { get; set; }
        public int Credits { get; set; }

        // Foreign key
        public int DepartmentID { get; set; }

        // Navigation properties
        public virtual Department Department { get; set; }
        public virtual ICollection<Instructor> Instructors { get; private set; }
    }

    public partial class OnlineCourse : Course
    {
        public string URL { get; set; }
    }

    public partial class OnsiteCourse : Course
    {
        public OnsiteCourse()
        {
            Details = new Details();
        }

        public Details Details { get; set; }
    }

    public class Details
    {
        public System.DateTime Time { get; set; }
        public string Location { get; set; }
        public string Days { get; set; }
    }

    public class Instructor
    {
        public Instructor()
        {
            this.Courses = new List<Course>();
        }

        // Primary key
        public int InstructorID { get; set; }
        public string LastName { get; set; }
        public string FirstName { get; set; }
        public System.DateTime HireDate { get; set; }

        // Navigation properties
        public virtual ICollection<Course> Courses { get; private set; }
    }

    public class OfficeAssignment
    {
        // Specifying InstructorID as a primary
        [Key()]
        public Int32 InstructorID { get; set; }

        public string Location { get; set; }

        // When the Entity Framework sees Timestamp attribute
        // it configures ConcurrencyCheck and DatabaseGeneratedPattern=Computed.
        [Timestamp]
        public Byte[] Timestamp { get; set; }

        // Navigation property
        public virtual Instructor Instructor { get; set; }
    }

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