使用Entity Framework DataLayer Repository Add（）函数的新记录

Question

I am beginner to Entity Framework and ASP.NET MVC and learning it from online tutorials, I made a class library datalayer ( Student.DataLayer ) first, in which I have a Repository.cs , where I have all the functions like

protected readonly ObjectContext _connection;
public Repository(IConnectionHelper connection)
{
    _connection = connection.Connection;
}

public virtual ObjectSet<T> ObjectSet
{
    get
    {
        return

        _connection.CreateObjectSet<T>();
    }
}

public virtual T Get(Expression<Func<T, bool>> predicate)
{
    return ObjectSet.FirstOrDefault(predicate);
}

    public virtual T Add(T entity)
    {
        ObjectSet.AddObject(entity);
        Save();
        return entity;
    }

    public virtual void Save()
    {
        _connection.SaveChanges();

     }

in IRepository.cs I have

public interface IRepository<T> where T : class
{
    T Get(Expression<Func<T, bool>> predicate);
    T Add(T entity);
    void Save();
}

Now I have add the reference of Student.Datalayer in the main ASP.NET MVC3 project Student , so I can access all the functions of datalayer now.

I have a table in database with the name Student , and it only have student_id and student_first_name and student_last_name columns

So far I have managed to update records in model which are already added

    public bool update_name(int id, string newfirstname, string newlastname)
    {
        var stud = _stu.Get(p => p.student_id == id);
         stud.student_first_name = newfirstname;
         stud.student_last_name = newlastname;
        _stu.Save();
        return true;
    }

but how to add a new record in the table using _stu.Add() , I can't figure this out. I am trying like below.

    public bool add_Student(string firstname, string lastname)
    {
       _stu.Add( //what to do here
       return true;
    }

I really want to know this way, because using datalayer like this approach, it's very clean. So please help me

Answer 1

The add_Student() function you have has no dependencies, ie., no parameters. I assume you would need some parameters like the students first and last name, maybe email address, etc.

And then use that to create a new student:

public bool add_Student(string firstname, string lastname)
{
    //Requires code to get the new ID, 
    //unless your ObjectSet classes creates the ID automatically.
    int newStudentID = 1; 

    var s = new StudentObject() 
    {
        id = newStudentID, //may not need to be here
        FirstName = firstname,
        LastName = lastname
    };

    _stu.Add(s)
    return true;
}