EF navigation properties not loaded when hooking into get method from partial class

I'm using the entity-framework with an asp.net mvc application and I'm using the database-first approach. I customized the code generation from the edmx a little to be able to hook into the get method of the properties of my entities like this:

public partial class CA
{
    private string _PropX;
    partial void OnGetPropX(ref string value);
    public string PropX
    {
        get
        {
            string value= _PropX;
            this.OnGetPropX(ref value);
            return value;
        }
        set
        {
            this._PropX= value;
        }
    }

    public virtual CB B { get; set; }
}

As you can see, there is also a navigation property to CB. In my non-generated partial cl开发者_开发问答ass A, I hook into the get method for PropX to return a property on CB like this:

public partial class CA
{
    partial void OnGetPropX(ref string value)
    {
        if(String.IsNullOrEmpty(value))
            value= this.B.PropY;  // Error
    }
}

But it turns out this.B is always Null in the line marked with // Error. However, if I create a new property in my non-generated partial class CA, like the following, everything works just fine:

public string MyPropX
{
    get
    {
        return (String.IsNullOrEmpty(this.PropX) ? this.B.PropY: this.PropX);
    }
}

Could anyone please explain this behaviour to me and perhaps tell me how to get the first method to work? Thanks!

---

Random guess...but perhaps changing your property to be non virtual prevents EF from creating proxies properly...try doing public virtual string PropX instead...