方法阻止我使用更新的值和不更新的表

Question

我遇到了奇怪的错误。我正在使用 SchoolInitializer 播种数据，但我将数据推送到 Student 表而不是 Employee 和 Course 表中。我在学生列表中添加了一个新学生，但我的表格没有更新，我的视图也没有显示新学生。但是，我删除了受保护的覆盖 void OnModelCreating(DbModelBuilder modelBuilder) 方法，并使用新学生、课程和注册数据更新了我的表，并且视图显示了适当的信息。这种方法有什么我一无所知的事情还是某种巧合？我不断关闭与数据库的连接，清理重建，并在没有调试的情况下运行。

namespace MyFirstWebApplication.Models
{
    public class SchoolInitializer : DropCreateDatabaseIfModelChanges<SchoolContext>
    {
        protected override void Seed(SchoolContext context)
        {
            var students = new List<Student>
            {
                new Student{FirstName = "James", LastName= "Dean", EnrollmentDate = DateTime.Parse("2014-01-02") },
                new Student{FirstName = "Lynda", LastName = "Thames", EnrollmentDate = DateTime.Parse("2013-11-02")}
            };

            foreach (var temp in students)
            {
                context.Students.Add(temp);
            }
            context.SaveChanges();

            var courses = new List<Course>
            {
                new Course{CourseName = "Java", TotalCredits = 4},
                new Course{CourseName = "C#", TotalCredits = 4}
            };

            foreach (var temp in courses)
            {
                context.Courses.Add(temp);
            }

            //context.SaveChanges();

            var enrollments = new List<Enrollment>
            {
                new Enrollment{StudentId = 1, CourseId = 1, Grade = 3},
                new Enrollment{StudentId = 1, CourseId = 2, Grade = 4}
            };

            foreach (var temp in enrollments)
            {
                context.Enrollments.Add(temp);
            }
            context.SaveChanges();

        }
    }
} 

namespace MyFirstWebApplication.Models
{
    public class SchoolContext : DbContext
    {   //enables CRUD functionality
        public DbSet<Student> Students { get; set; }
        public DbSet<Course> Courses { get; set; }
        public DbSet<Enrollment> Enrollments { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
        }
    }
}

Answer 1

打开 Visual Studio 窗口，确保在 SchoolContext.OnModelBuilder 方法中没有注释掉任何内容...

1. VS 打开，按Ctrl + Q
2. 输入Package Manager Console然后回车
3. 在应该出现的输出选项卡上，输入Update-Database

EntityFramework 应该做它的事情，并且你的值应该弹出

---

您还缺少 ConnectionString，这会导致您遇到与您列出的问题类似的奇怪问题...

确保您在我们的 App.Config 或 Web.Config...中有此设置...

<connectionStrings>
   <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=SchoolEtc;Integrated Security=True"
  providerName="System.Data.SqlClient" />
</connectionStrings>

接下来我需要你回到你身边SchoolContextclass

public class SchoolContext : DbContext
{
    public SchoolContext() : base("DefaultConnection")
    {}

   //enables CRUD functionality
    public DbSet<Student> Students { get; set; }
    public DbSet<Course> Courses { get; set; }
    public DbSet<Enrollment> Enrollments { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
    }
}

在你完成之后......

1. 输入此快捷方式CTRL + Q... 输入Package Manager Console
2. 输入Enable-Migrations
3. 输入Add-Migration InitialMigration
4. 输入Update-Database

之后您应该会看到更改。