No se puede insertar la clave duplicada en el objeto 'dbo.User'. \ R \ nLa sentencia ha finalizado

Question

Tengo una tabla de usuario. hay referencias a esta tabla de otras tablas para campos como CreatedBy.

El problema es que cuando inserto una fila de otra tabla (digamos 'x'), intenta insertar un nuevo usuario en la tabla de usuarios.

Lo que debería hacer es insertar una fila en la tabla 'x' con CreatedBy como el usuario existente.

Usando Entity Framework 4. ¿Alguien se ha enfrentado a un problema como ese anteriormente?

Answer 1

Puede insertar una entidad junto con entidades relacionadas o puede insertar una entidad sin las entidades relacionadas, solo haciendo referencia a las existentes. Depende del código que escribas.

Ejemplo 1:

User user = GetUserFromSomewhere(); 
using (var context = new MyContext()) 
{ 
    Order order = new Order(); 
    order.CreatedBy = user; 

    context.Orders.AddObject(order); 
    // will put both order and related entity user into Added state 
    // because user is not attached to the context 

    context.SaveChanges(); 
    // creates new order and new user and sets the relationship between them 
} 

Ejemplo 2:

using (var context = new MyContext()) 
{ 
    User user = context.Users.SingleOrDefault(u => u.Id == 1); 
    // query attaches this user to this context 
    // user is in state Unchanged now 

    Order order = new Order(); 
    order.CreatedBy = user; 

    context.Orders.AddObject(order); 
    // will put the order into Added state but doesn't touch the 
    // state of already attached related entities -> user remains 
    // in state Unchanged 

    context.SaveChanges(); 
    // creates new order with reference to user, but doesn't create new user 
} 

Ejemplo 3:

User user = GetUserFromSomewhere(); 
using (var context = new MyContext()) 
{ 
    context.Users.Attach(user); 
    // we attach explicitely to the context telling EF thereby 
    // that we know that this user exists in the DB 
    // user is in state Unchanged now 

    Order order = new Order(); 
    order.CreatedBy = user; 

    context.Orders.AddObject(order); 
    // will put the order into Added state but doesn't touch the 
    // state of already attached related entities -> user remains 
    // in state Unchanged 

    context.SaveChanges(); 
    // creates new order with reference to user, but doesn't create new user 
} 

Editar

Ejemplo 4:

int userId = GetUserIdFromSomewhere(); 
using (var context = new MyContext()) 
{ 
    var user = new User { Id = userId }; 
    // we create a stub user entity with the correct primary key 
    // It's not necessary to set other properties 
    // to only set the relationship to the order 

    context.Users.Attach(user); 
    // we attach explicitely to the context telling EF thereby 
    // that we know that this user exists in the DB 
    // user is in state Unchanged now 

    Order order = new Order(); 
    order.CreatedBy = user; 

    context.Orders.AddObject(order); 
    // will put the order into Added state but doesn't touch the 
    // state of already attached related entities -> user remains 
    // in state Unchanged 

    context.SaveChanges(); 
    // creates new order with reference to user, but doesn't create new user 
}