#27 Increase the speed of SelectedObject

[Davide]

I have changed the get of SelectedObject, this permit to increase the speed. The proposed version that I have tested is:

    public virtual Object SelectedObject {
        get {
            return this.SelectedIndex >= 0 ? this.GetModelObject(this.SelectedIndex) : null;
        }
        set {
          ...
        }
    }