实体框架教程（简单的代码优先示例）不起作用

Question

Today I started following an Entity Framework tutorial: Simple Code First Example

I think I have everything how it should be, but my application doesn't work.

Here's my code:

public class Student
{
    public Student()
    {

    }
    public int StudentID { get; set; }
    public string StudentName { get; set; }
    public DateTime DateOfBirth { get; set; }
    public byte[] Photo { get; set; }
    public decimal Height { get; set; }
    public float Weight { get; set; }

    public Standard Standard { get; set; }
}

public class Standard
    {
        public Standard()
        {

        }
        public int StandardId { get; set; }
        public string StandardName { get; set; }

        public ICollection<Student> Students { get; set; }
    }

public class SchoolContext : DbContext
{
    public SchoolContext()
        : base()
    {

    }

    public DbSet<Student> Students { get; set; }
    public DbSet<Standard> Standards { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        using (var ctx = new SchoolContext())
        {
            Student stud = new Student() { StudentName = "New Student" };

            ctx.Students.Add(stud);
            ctx.SaveChanges();
            Console.WriteLine("done.");
        }
    }
}

It builds without any errors or warnings, console starts, but it doesn't go past

ctx.Students.Add(stud);

It also didn't create any database and tables.

I followed everything from the tutorial, and have no idea why it doesn't work.

EDIT: It does throw an errorafter 60 seconds (Additional information are in polish, I don't really now how to change it to english in VS): An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in EntityFramework.dll

Additional information: Wystąpił błąd związany z siecią lub wystąpieniem podczas ustanawiania połączenia z serwerem programu SQL Server. Nie można odnaleźć serwera lub jest on niedostępny. Sprawdź, czy nazwa wystąpienia jest poprawna i czy konfiguracja serwera programu SQL Server zezwala na połączenia zdalne. (provider: SQL Network Interfaces, error: 26 - Błąd podczas lokalizowania określonego serwera/wystąpienia)

And I have to add, I'm using Visual Studio 2013 Community and the localDB which is included in this version of visual studio.

Answer 1

Did you try to make your navigation properties as virtual? Also if you want to connect this two Student and Standard class to each other you need to define foreign keys.

For example add this in Student class:

public class Student
{
    public Student()
    {

    }
    public int StudentID { get; set; }
    public string StudentName { get; set; }
    public DateTime DateOfBirth { get; set; }
    public byte[] Photo { get; set; }
    public decimal Height { get; set; }
    public float Weight { get; set; }

    public int StandartID{get;set;}//foreign key references Standard(StandardId)
    public virtual Standard Standard { get; set; }//navigation property
}

And this in Stadart class:

public class Standard
{
    public Standard()
    {

    }
    public int StandardId { get; set; }
    public string StandardName { get; set; }

    public int StudentID{get;set;}//foreign key references Student(StudentID)
    public virtual ICollection<Student> Students { get; set; }
}

Hope this will help you