Entity framework can't add with singleton

问题

My persons class:

 public class User
{
    public int Id { get; private set; }

    public string Isim { get; set; }

    public string Soyad { get; set; }

    public User(string isim, string soyad)
    {
        Isim = isim;
        Soyad = soyad;
    }
}

My UserBusiness class:

public sealed class UserBusiness
{
    JuqueryDbEntities entity = new JuqueryDbEntities();

    private static volatile UserBusiness instance;
    private static readonly object syncRoot = new Object();

    private UserBusiness() { }

    public static UserBusiness Instance
    {
        get
        {
            if (instance == null)
            {
                lock (syncRoot)
                {
                    if (instance == null)
                        instance = new UserBusiness();
                }
            }

            return instance;
        }
    }

    public void AddUser(User userToAdd)
    {
        entity.PersonelTable.Add(userToAdd);
        entity.SaveChanges();
    }
}

And lastly my webform codebehind onclick of a login button:

protected void Button1_Click(object sender, EventArgs e)
    {
        string isim = TextBox1.Text;
        string soyad = TextBox2.Text;
        var newUser = new User(isim, soyad);
        UserBusiness.Instance.AddUser(newUser);  
    }

Here is my problem: I get an error in AddUser method of my UserBusiness class. An error in 'entity.PersonelTable.Add(newUser);' line says 'The best overload method match for 'System.Data.Entity.DbSet.Add(SuperQquery.PersonelTable)' has some invalid arguments.' What am I doing wrong(Btw my Id is autoincrement so I am not setting it any value.)

回答1:

your problem here is that the method Add of System.Data.Entity.DbSet does simply not take argument of type user. like mentioned in the error

System.Data.Entity.DbSet.Add(SuperQquery.PersonelTable)' has some invalid arguments

it takes objects of type SuperQquery.PersonelTable

So what you need to do is change AddUser method

public void AddUser(User userToAdd)
{
   SuperQquery.PersonelTable pt = new SuperQquery.PersonelTable();
   pt.FieldName1 = userToAdd.Isim;
   pt.FieldName2 = userToAdd.Soyad;

   entity.PersonelTable.Add(pt);
   entity.SaveChanges();
}

where FieldName are names of columns in the table of the database

EDIT: if this works, we can say that you made a conversion of type user to type SuperQquery.PersonelTable the way you can insert data in database, but the best way here is to change the class User by a new class PersonelTable with the same logic. No need to do a conversion.

来源：https://stackoverflow.com/questions/36747614/entity-framework-cant-add-with-singleton

标签

ASP.NET

entity-framework

oop

singleton