实体框架和ICollection

Question

Background

I'm in the process of learning WPF (for fun mostly) and am building a little app to use.

I've created a SQL Server Database (Tables only), and then used Entity Framework (EF) 'Code First from Database' to generate the DB Context and associated Model classes.

The Problem / Misunderstanding

I have a Table which is referenced in another Table, so EF generates a class with an ICollection of the child objects (table names etc modified for simplicity) :

[Table("Parent")]
public partial class Parent
{
   //Other Properties etc

   public virtual ICollection<Child> Children { get; set; }
}

Questions

1. I want to modify an Item within the 'Children' ICollection to just test my understanding of the process and check that it works, but there seems no easy way to do this; there is no .Item( int x ) method (is the intention that this ICollection is 'for reference only' and that a separate query has to be made?)

or is there some other way to do it?

2. Not having delved to much into WPF DataBinding as yet, is it possible to bind this ICollection to a control on a form and have the user manipulate the data which I can then take and save the changes to the DB?

Answer 1

I would prefer to be in control of the Navigation properties vs leaving it up to EF. Modify the class to the following:

[Table("Parent")]
public partial class Parent
{
    private List<Child> _children;

    public Parent()
    {
        _children = new List<Child>();
    }

    // other properties, etc.

    public List<Child> Children
    {
        get { return _children; }
        set { _children = value; }
    }
}

As far as DataBinding is concerned, you can easily bind the ItemsSource of any ItemsControl to the Child collection. For example:

<ComboBox ItemsSource="{Binding Path=Children}" />

The above example assumes your relative DataContext is set to your Parent object.

Answer 2

As far i understand , Pls Look if this helps you.

using (var db = new DataBaseEntity())
{
    Child myChild = db.Parent.Select(x => x.Child);

    myChild.IsSelected = true;
    myChild.Name = "MyChildName";

    db.SaveChanges() //EF Tracks the items so u could simple commit the changes to Db.
 }

Second question:

I don't think You could directly bind ICollection into WPf ItemSource. Try a DTO or Serialize them into Observable Collection Like this.

ObservableCollection<Child> childCollection = new ObservableCollection<Child>();
_childCollection .Add(new Child
       { 
           // Serialize to Properties in the Child 
       });

// Bind the collection or property where u need
<List ItemSource="{Binding _ChildCollection}" />