【EF6学习笔记】（五）数据库迁移及部署

原文地址：Code First Migrations and Deployment

原文主要讲两部分：开发环境下数据库迁移到其他数据库服务器；以及在Azure上如何部署应用；

迁移数据库

原文前面讲一堆内容，主要就是说数据库在开发过程中，如果数据模型经常需要调整，那么数据库每次都删除重建有点不太现实；尤其是对于已部署的正式环境，需要的仅仅是数据库升级，而不可能直接Drop掉，再重新Create.

所以，需要启用EF的数据迁移功能。

原文为了演示效果更好，就直接演示了迁移升级到一个全新的数据库中：

第1步：把Web.config文件中 entityFramework节点下 contexts注释掉：

  <entityFramework>
    <!--<contexts>
      <context type="EFTest.DAL.SchoolContext, EFTest">
        <databaseInitializer type="EFTest.DAL.SchoolInitializer, EFTest" />
      </context>
    </contexts>-->
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="mssqllocaldb" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>

第2步：数据库连接字符串中，数据库名改个名字，比如EFTest2

<connectionStrings>
    <add name="SchoolContext" connectionString="Data Source=(localdb)\ProjectsV13;Initial Catalog=EFTest2;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=True;ApplicationIntent=ReadWrite;MultiSubnetFailover=False;" providerName="System.Data.SqlClient" />
  </connectionStrings>

第3步：打开PM控制台：

第4步：先执行 enable-migrations , 会创建一个Migrations子目录，并多出一个Configuration.cs文件；

再执行 add-migration InitialCreate , 会在Migrations子目录创建一个带时间戳的 xxxxxxxxxx_InitialCreate文件；

第5步，在Configuration.cs文件有个Seed方法就是用来初始化数据库的时候放入的种子数据；可以如以下方式加入数据：

在这个要注意，Seed方法在后面执行update-database命令的时候会被执行，而且每次执行update-database命令的时候都会执行；

所以这个地方需要用AddOrUpdate来处理一些种子数据，防止插入重复数据；

另外，注意一些外键数据，例如是数据库自增长的列，则需要前面先保存的数据到数据库，然后才用ID这属性值（不然ID是没数据的）

namespace EFTest.Migrations
{
    using Models;
    using System;
    using System.Collections.Generic;
    using System.Data.Entity;
    using System.Data.Entity.Migrations;
    using System.Linq;

    internal sealed class Configuration : DbMigrationsConfiguration<EFTest.DAL.SchoolContext>
    {
        public Configuration()
        {
            AutomaticMigrationsEnabled = false;
        }

        protected override void Seed(EFTest.DAL.SchoolContext context)
        {
            //  This method will be called after migrating to the latest version.

            //  You can use the DbSet<T>.AddOrUpdate() helper extension method 
            //  to avoid creating duplicate seed data. E.g.
            //
            //    context.People.AddOrUpdate(
            //      p => p.FullName,
            //      new Person { FullName = "Andrew Peters" },
            //      new Person { FullName = "Brice Lambson" },
            //      new Person { FullName = "Rowan Miller" }
            //    );
            //

            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("2005-08-11") }
            };
            students.ForEach(s => context.Students.AddOrUpdate(p => p.LastName, s));
            context.SaveChanges();

            var courses = new List<Course>
            {
                new Course {CourseID = 1050, Title = "Chemistry",      Credits = 3, },
                new Course {CourseID = 4022, Title = "Microeconomics", Credits = 3, },
                new Course {CourseID = 4041, Title = "Macroeconomics", Credits = 3, },
                new Course {CourseID = 1045, Title = "Calculus",       Credits = 4, },
                new Course {CourseID = 3141, Title = "Trigonometry",   Credits = 4, },
                new Course {CourseID = 2021, Title = "Composition",    Credits = 3, },
                new Course {CourseID = 2042, Title = "Literature",     Credits = 4, }
            };
            courses.ForEach(s => context.Courses.AddOrUpdate(p => p.Title, s));
            context.SaveChanges();

            var enrollments = new List<Enrollment>
            {
                new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Alexander").ID,
                    CourseID = courses.Single(c => c.Title == "Chemistry" ).CourseID,
                    Grade = Grade.A
                },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Alexander").ID,
                    CourseID = courses.Single(c => c.Title == "Microeconomics" ).CourseID,
                    Grade = Grade.C
                 },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Alexander").ID,
                    CourseID = courses.Single(c => c.Title == "Macroeconomics" ).CourseID,
                    Grade = Grade.B
                 },
                 new Enrollment {
                     StudentID = students.Single(s => s.LastName == "Alonso").ID,
                    CourseID = courses.Single(c => c.Title == "Calculus" ).CourseID,
                    Grade = Grade.B
                 },
                 new Enrollment {
                     StudentID = students.Single(s => s.LastName == "Alonso").ID,
                    CourseID = courses.Single(c => c.Title == "Trigonometry" ).CourseID,
                    Grade = Grade.B
                 },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Alonso").ID,
                    CourseID = courses.Single(c => c.Title == "Composition" ).CourseID,
                    Grade = Grade.B
                 },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Anand").ID,
                    CourseID = courses.Single(c => c.Title == "Chemistry" ).CourseID
                 },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Anand").ID,
                    CourseID = courses.Single(c => c.Title == "Microeconomics").CourseID,
                    Grade = Grade.B
                 },
                new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Barzdukas").ID,
                    CourseID = courses.Single(c => c.Title == "Chemistry").CourseID,
                    Grade = Grade.B
                 },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Li").ID,
                    CourseID = courses.Single(c => c.Title == "Composition").CourseID,
                    Grade = Grade.B
                 },
                 new Enrollment {
                    StudentID = students.Single(s => s.LastName == "Justice").ID,
                    CourseID = courses.Single(c => c.Title == "Literature").CourseID,
                    Grade = Grade.B
                 }
            };

            foreach (Enrollment e in enrollments)
            {
                var enrollmentInDataBase = context.Enrollments.Where(
                    s =>
                         s.Student.ID == e.StudentID &&
                         s.Course.CourseID == e.CourseID).SingleOrDefault();
                if (enrollmentInDataBase == null)
                {
                    context.Enrollments.Add(e);
                }
            }
            context.SaveChanges();
        }
    }
}