在前面的教程中，我们使用了一个简单的数据模型，包括三个数据实体。在这个教程汇中，我们将添加更多的实体和关系，按照特定的格式和验证规则等自定义数据模型。

Contoso大学校园管理系统的数据模型如下。

 一、修改学生实体

1.DataType Attribute

using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

namespace ContosoUniversity.Models

{

    public class Student

    {

        public int StudentID { get; set; }

        public string LastName { get; set; }

        public string FirstMidName { get; set; }

        [DataType(DataType.Date)]

        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

        public DateTime EnrollmentDate { get; set; }

        public virtual ICollection<Enrollment> Enrollments { get; set; }

    }

}

DataType.Date定义了日期显示不包括时间。DataType的枚举定义了很多类型，比如Date、Time、PhoneNumber、Currency、EmailAddress等。它并不包含验证规则。

DisplayFormat属性用来显式指定日期格式，ApplyFormatInEditMode设置指定将当前格式应用到，值显示在可编辑的文本框中。

2.StringLengthAttribute

using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

namespace ContosoUniversity.Models

{

    public class Student

    {

        public int StudentID { get; set; }

        [StringLength()]

        public string LastName { get; set; }

        [StringLength(, ErrorMessage = "First name cannot be longer than 50 characters.")]

        public string FirstMidName { get; set; }

        [DataType(DataType.Date)]

        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

        public DateTime EnrollmentDate { get; set; }

        public virtual ICollection<Enrollment> Enrollments { get; set; }

    }

}

StringLength规定字符串长度必须在某个值内，但是不会阻止用户提交空的字段值。复杂的验证规则可以使用正则表达式验证RegularExpression属性。

3.列属性

using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models

{

    public class Student

    {

        public int StudentID { get; set; }

        [StringLength()]

        public string LastName { get; set; }

        [StringLength(, ErrorMessage = "First name cannot be longer than 50 characters.")]

        [Column("FirstName")]

        public string FirstMidName { get; set; }

        [DataType(DataType.Date)]

        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

        public DateTime EnrollmentDate { get; set; }

        public virtual ICollection<Enrollment> Enrollments { get; set; }

    }

}

FirstMidName属性对应到数据库中的列字段名为FirstName。

二、创建老师Instructor实体 

using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models

{

    public class Instructor

    {

        public int InstructorID { get; set; }

        [Required]

        [Display(Name = "Last Name")]

        [StringLength()]

        public string LastName { get; set; }

        [Required]

        [Column("FirstName")]

        [Display(Name = "First Name")]

        [StringLength()]

        public string FirstMidName { get; set; }

        [DataType(DataType.Date)]

        [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

        [Display(Name = "Hire Date")]

        public DateTime HireDate { get; set; }

        public string FullName

        {

            get { return LastName + ", " + FirstMidName; }

        }

        public virtual ICollection<Course> Courses { get; set; }

        public virtual OfficeAssignment OfficeAssignment { get; set; }

    }

}

你可以在一行上放入多个属性。

public class Instructor

{

   public int InstructorID { get; set; }

   [Display(Name = "Last Name"),StringLength(, MinimumLength=)]

   public string LastName { get; set; }

   [Column("FirstName"),Display(Name = "First Name"),StringLength(, MinimumLength=)]

   public string FirstMidName { get; set; }

   [DataType(DataType.Date),Display(Name = "Hire Date"),DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

   public DateTime HireDate { get; set; }

   public string FullName

   {

      get { return LastName + ", " + FirstMidName; }

   }

   public virtual ICollection<Course> Courses { get; set; }

   public virtual OfficeAssignment OfficeAssignment { get; set; }

}

FullName是一个计算属性，它返回连接两个属性的值，只有get，在数据库中并不创建列字段。

三、创建办公地点OfficeAssignment实体

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models

{

    public class OfficeAssignment

    {

        [Key]

        [ForeignKey("Instructor")]

        public int InstructorID { get; set; }

        [StringLength()]

        [Display(Name = "Office Location")]

        public string Location { get; set; }

        public virtual Instructor Instructor { get; set; }

    }

}

InstructorID是主键也是教师实体的外键，因为InstructorID不能识别为主键，主键必须是类名ID或者ID，所以需要加[Key]。

四、修改课程Course实体

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models

{

   public class Course

   {

      [DatabaseGenerated(DatabaseGeneratedOption.None)]

      [Display(Name = "Number")]

      public int CourseID { get; set; }

      [StringLength(, MinimumLength = )]

      public string Title { get; set; }

      [Range(, )]

      public int Credits { get; set; }

      [Display(Name = "Department")]

      public int DepartmentID { get; set; }

public virtual Department Department { get; set; }

      public virtual ICollection<Enrollment> Enrollments { get; set; }

      public virtual ICollection<Instructor> Instructors { get; set; }

   }

}

五、创建系部Department实体

using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models

{

   public class Department

   {

      public int DepartmentID { get; set; }

      [StringLength(, MinimumLength=)]

      public string Name { get; set; }

      [DataType(DataType.Currency)]

      [Column(TypeName = "money")]

      public decimal Budget { get; set; }

      [DataType(DataType.Date)]

      public DateTime StartDate { get; set; }

      [Display(Name = "Administrator")]

      public int? InstructorID { get; set; }

      public virtual Instructor Administrator { get; set; }

      public virtual ICollection<Course> Courses { get; set; }

   }

}

Column属性改变了列字段的类型。
六、修改学生Student实体

using System;

using System.Collections.Generic;

using System.ComponentModel.DataAnnotations;

using System.ComponentModel.DataAnnotations.Schema;

namespace ContosoUniversity.Models

{

   public class Student

   {

      public int StudentID { get; set; }

      [StringLength(, MinimumLength = )]

      public string LastName { get; set; }

      [StringLength(, MinimumLength = , ErrorMessage = "First name cannot be longer than 50 characters.")]

      [Column("FirstName")]

      public string FirstMidName { get; set; }

      [DataType(DataType.Date)]

      [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]

      [Display(Name = "Enrollment Date")]

      public DateTime EnrollmentDate { get; set; }

      public string FullName

      {

         get { return LastName + ", " + FirstMidName; }

      }

      public virtual ICollection<Enrollment> Enrollments { get; set; }

   }

}

七、修改注册Enrollment实体

using System.ComponentModel.DataAnnotations;

namespace ContosoUniversity.Models

{

    public enum Grade

    {

        A, B, C, D, F

    }

    public class Enrollment

    {

        public int EnrollmentID { get; set; }

        public int CourseID { get; set; }

        public int StudentID { get; set; }

        [DisplayFormat(NullDisplayText = "No grade")]

        public Grade? Grade { get; set; }

        public virtual Course Course { get; set; }

        public virtual Student Student { get; set; }

    }

}

 八、使用Seed方法为数据库注入测试数据

namespace ContosoUniversity.Migrations

{

   using System;

   using System.Collections.Generic;

   using System.Data.Entity;

   using System.Data.Entity.Migrations;

   using System.Linq;

   using ContosoUniversity.Models;

   using ContosoUniversity.DAL;

   internal sealed class Configuration : DbMigrationsConfiguration<SchoolContext>

   {

      public Configuration()

      {

         AutomaticMigrationsEnabled = false;

      }

      protected override void Seed(SchoolContext context)

      {

         var students = new List<Student>

            {

                new Student { FirstMidName = "Carson",   LastName = "Alexander",

                    EnrollmentDate = DateTime.Parse("2010-09-01") },

                new Student { FirstMidName = "Meredith", LastName = "Alonso",

                    EnrollmentDate = DateTime.Parse("2012-09-01") },

                new Student { FirstMidName = "Arturo",   LastName = "Anand",

                    EnrollmentDate = DateTime.Parse("2013-09-01") },

                new Student { FirstMidName = "Gytis",    LastName = "Barzdukas",

                    EnrollmentDate = DateTime.Parse("2012-09-01") },

                new Student { FirstMidName = "Yan",      LastName = "Li",

                    EnrollmentDate = DateTime.Parse("2012-09-01") },

                new Student { FirstMidName = "Peggy",    LastName = "Justice",

                    EnrollmentDate = DateTime.Parse("2011-09-01") },

                new Student { FirstMidName = "Laura",    LastName = "Norman",

                    EnrollmentDate = DateTime.Parse("2013-09-01") },

                new Student { FirstMidName = "Nino",     LastName = "Olivetto",

                    EnrollmentDate = DateTime.Parse("2005-09-01") }

            };

         students.ForEach(s => context.Students.AddOrUpdate(p => p.LastName, s));

         context.SaveChanges();

         var instructors = new List<Instructor>

            {

                new Instructor { FirstMidName = "Kim",     LastName = "Abercrombie",

                    HireDate = DateTime.Parse("1995-03-11") },

                new Instructor { FirstMidName = "Fadi",    LastName = "Fakhouri",

                    HireDate = DateTime.Parse("2002-07-06") },

                new Instructor { FirstMidName = "Roger",   LastName = "Harui",

                    HireDate = DateTime.Parse("1998-07-01") },

                new Instructor { FirstMidName = "Candace", LastName = "Kapoor",

                    HireDate = DateTime.Parse("2001-01-15") },

                new Instructor { FirstMidName = "Roger",   LastName = "Zheng",

                    HireDate = DateTime.Parse("2004-02-12") }

            };

         instructors.ForEach(s => context.Instructors.AddOrUpdate(p => p.LastName, s));

         context.SaveChanges();

         var departments = new List<Department>

            {

                new Department { Name = "English",     Budget = ,

                    StartDate = DateTime.Parse("2007-09-01"),

                    InstructorID  = instructors.Single( i => i.LastName == "Abercrombie").InstructorID },

                new Department { Name = "Mathematics", Budget = ,

                    StartDate = DateTime.Parse("2007-09-01"),

                    InstructorID  = instructors.Single( i => i.LastName == "Fakhouri").InstructorID },

                new Department { Name = "Engineering", Budget = ,

                    StartDate = DateTime.Parse("2007-09-01"),

                    InstructorID  = instructors.Single( i => i.LastName == "Harui").InstructorID },

                new Department { Name = "Economics",   Budget = ,

                    StartDate = DateTime.Parse("2007-09-01"),

                    InstructorID  = instructors.Single( i => i.LastName == "Kapoor").InstructorID }

            };

         departments.ForEach(s => context.Departments.AddOrUpdate(p => p.Name, s));

         context.SaveChanges();

         var courses = new List<Course>

            {

                new Course {CourseID = , Title = "Chemistry",      Credits = ,

                  DepartmentID = departments.Single( s => s.Name == "Engineering").DepartmentID,

                  Instructors = new List<Instructor>()

                },

                new Course {CourseID = , Title = "Microeconomics", Credits = ,

                  DepartmentID = departments.Single( s => s.Name == "Economics").DepartmentID,

                  Instructors = new List<Instructor>()

                },

                new Course {CourseID = , Title = "Macroeconomics", Credits = ,

                  DepartmentID = departments.Single( s => s.Name == "Economics").DepartmentID,

                  Instructors = new List<Instructor>()

                },

                new Course {CourseID = , Title = "Calculus",       Credits = ,

                  DepartmentID = departments.Single( s => s.Name == "Mathematics").DepartmentID,

                  Instructors = new List<Instructor>()

                },

                new Course {CourseID = , Title = "Trigonometry",   Credits = ,

                  DepartmentID = departments.Single( s => s.Name == "Mathematics").DepartmentID,

                  Instructors = new List<Instructor>()

                },

                new Course {CourseID = , Title = "Composition",    Credits = ,

                  DepartmentID = departments.Single( s => s.Name == "English").DepartmentID,

                  Instructors = new List<Instructor>()

                },

                new Course {CourseID = , Title = "Literature",     Credits = ,

                  DepartmentID = departments.Single( s => s.Name == "English").DepartmentID,

                  Instructors = new List<Instructor>()

                },

            };

         courses.ForEach(s => context.Courses.AddOrUpdate(p => p.CourseID, s));

         context.SaveChanges();

         var officeAssignments = new List<OfficeAssignment>

            {

                new OfficeAssignment {

                    InstructorID = instructors.Single( i => i.LastName == "Fakhouri").InstructorID,

                    Location = "Smith 17" },

                new OfficeAssignment {

                    InstructorID = instructors.Single( i => i.LastName == "Harui").InstructorID,

                    Location = "Gowan 27" },

                new OfficeAssignment {

                    InstructorID = instructors.Single( i => i.LastName == "Kapoor").InstructorID,

                    Location = "Thompson 304" },

            };

         officeAssignments.ForEach(s => context.OfficeAssignments.AddOrUpdate(p => p.Location, s));

         context.SaveChanges();

         AddOrUpdateInstructor(context, "Chemistry", "Kapoor");

         AddOrUpdateInstructor(context, "Chemistry", "Harui");

         AddOrUpdateInstructor(context, "Microeconomics", "Zheng");

         AddOrUpdateInstructor(context, "Macroeconomics", "Zheng");

         AddOrUpdateInstructor(context, "Calculus", "Fakhouri");

         AddOrUpdateInstructor(context, "Trigonometry", "Harui");

         AddOrUpdateInstructor(context, "Composition", "Abercrombie");

         AddOrUpdateInstructor(context, "Literature", "Abercrombie");

         context.SaveChanges();

         var enrollments = new List<Enrollment>

            {

                new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Alexander").StudentID,

                    CourseID = courses.Single(c => c.Title == "Chemistry" ).CourseID,

                    Grade = Grade.A

                },

                 new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Alexander").StudentID,

                    CourseID = courses.Single(c => c.Title == "Microeconomics" ).CourseID,

                    Grade = Grade.C

                 },

                 new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Alexander").StudentID,

                    CourseID = courses.Single(c => c.Title == "Macroeconomics" ).CourseID,

                    Grade = Grade.B

                 },

                 new Enrollment {

                     StudentID = students.Single(s => s.LastName == "Alonso").StudentID,

                    CourseID = courses.Single(c => c.Title == "Calculus" ).CourseID,

                    Grade = Grade.B

                 },

                 new Enrollment {

                     StudentID = students.Single(s => s.LastName == "Alonso").StudentID,

                    CourseID = courses.Single(c => c.Title == "Trigonometry" ).CourseID,

                    Grade = Grade.B

                 },

                 new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Alonso").StudentID,

                    CourseID = courses.Single(c => c.Title == "Composition" ).CourseID,

                    Grade = Grade.B

                 },

                 new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Anand").StudentID,

                    CourseID = courses.Single(c => c.Title == "Chemistry" ).CourseID

                 },

                 new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Anand").StudentID,

                    CourseID = courses.Single(c => c.Title == "Microeconomics").CourseID,

                    Grade = Grade.B

                 },

                new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Barzdukas").StudentID,

                    CourseID = courses.Single(c => c.Title == "Chemistry").CourseID,

                    Grade = Grade.B

                 },

                 new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Li").StudentID,

                    CourseID = courses.Single(c => c.Title == "Composition").CourseID,

                    Grade = Grade.B

                 },

                 new Enrollment {

                    StudentID = students.Single(s => s.LastName == "Justice").StudentID,

                    CourseID = courses.Single(c => c.Title == "Literature").CourseID,

                    Grade = Grade.B

                 }

            };

         foreach (Enrollment e in enrollments)

         {

            var enrollmentInDataBase = context.Enrollments.Where(

                s =>

                     s.Student.StudentID == e.StudentID &&

                     s.Course.CourseID == e.CourseID).SingleOrDefault();

            if (enrollmentInDataBase == null)

            {

               context.Enrollments.Add(e);

            }

         }

         context.SaveChanges();

      }

      void AddOrUpdateInstructor(SchoolContext context, string courseTitle, string instructorName)

      {

         var crs = context.Courses.SingleOrDefault(c => c.Title == courseTitle);

         var inst = crs.Instructors.SingleOrDefault(i => i.LastName == instructorName);

         if (inst == null)

            crs.Instructors.Add(context.Instructors.Single(i => i.LastName == instructorName));

      }

   }

}

 九、模型迁移

在PMC, 输入add-migration命令:

PM> add-Migration Chap4

此时更新数据库，可能会得到如下错误：

The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Course_dbo.Department_DepartmentID". The conflict occurred in database "ContosoUniversity", table "dbo.Department", column 'DepartmentID'.

编辑<timestamp>_Chap4.cs模型迁移文件, 修改代码如下：

CreateTable(

        "dbo.CourseInstructor",

        c => new

            {

                CourseID = c.Int(nullable: false),

                InstructorID = c.Int(nullable: false),

            })

        .PrimaryKey(t => new { t.CourseID, t.InstructorID })

        .ForeignKey("dbo.Course", t => t.CourseID, cascadeDelete: true)

        .ForeignKey("dbo.Instructor", t => t.InstructorID, cascadeDelete: true)

        .Index(t => t.CourseID)

        .Index(t => t.InstructorID);

    // Create  a department for course to point to.

    Sql("INSERT INTO dbo.Department (Name, Budget, StartDate) VALUES ('Temp', 0.00, GETDATE())");

    //  default value for FK points to department created above.

    AddColumn("dbo.Course", "DepartmentID", c => c.Int(nullable: false, defaultValue: ));

    //AddColumn("dbo.Course", "DepartmentID", c => c.Int(nullable: false));

    AlterColumn("dbo.Course", "Title", c => c.String(maxLength: ));

    AddForeignKey("dbo.Course", "DepartmentID", "dbo.Department", "DepartmentID", cascadeDelete: true);

    CreateIndex("dbo.Course", "DepartmentID");

}

public override void Down()

{

(确保你已经删除了多余的AddColumn，如果迁移不成功，可将数据库删除后再试。)

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