Cannot get relationship to update for navigation properties in entity framework

Question

I am currently using EF4.3 and Code First. Creation of my objects works (via my views - just using the auto-generated Create), but when I attempt to edit an object, it does

Answer 1

There are several options here, I will list 3 of them:

Option 1: Using GraphDiff

*This needs the Configuration.AutoDetectChangesEnabled of your context set to true.

Just install GraphDiff with NuGet

Install-Package RefactorThis.GraphDiff

Then

using (var context = new Context())
{
    var customer = new Customer()
    {
        Id = 12503,
        Name = "Jhon Doe",
        City = new City() { Id = 8, Name = "abc" }
    };

    context.UpdateGraph(customer, map => map.AssociatedEntity(p => p.City));
    context.Configuration.AutoDetectChangesEnabled = true;

    context.SaveChanges();
}

For more details about GraphDiff look here.

Option 2: Find and Edit

Searching your entity with EF to track it to the context. Then edit the properties.

*This needs the Configuration.AutoDetectChangesEnabled of your context set to true.

var customer = new Customer()
{
    Id = 12503,
    Name = "Jhon Doe",
    City = new City() { Id = 8, Name = "abc" }
};

using (var context = new Contexto())
{
    var customerFromDatabase = context.Customers
                                      .Include(x => x.City)
                                      .FirstOrDefault(x => x.Id == customer.Id);

    var cityFromDataBase = context.Cities.FirstOrDefault(x => x.Id == customer.City.Id);

    customerFromDatabase.Name = customer.Name;
    customerFromDatabase.City = cityFromDataBase;                

    context.Configuration.AutoDetectChangesEnabled = true;
    context.SaveChanges();
}

Option 3: Using a scalar property

In a matter of performance this is the best way, but it mess your class with database concerns. Because you will need to create a scalar (primitive type) property to map the Id.

*In this way there is no need to set the Configuration.AutoDetectChangesEnabled to true. And also you won't need to do a query to the database to retrieve the entities (as the first two options would - yes GraphDiff does it behind the scenes!).

var customer = new Customer()
{
    Id = 12503,
    Name = "Jhon Doe",
    City_Id = 8,
    City = null
};

using (var contexto = new Contexto())
{
    contexto.Entry(customer).State = EntityState.Modified;
    contexto.SaveChanges();
}