how to use an object in other page wpf

How can I use an object from a WPF page to an other WPF page?

ProductBactlog Page

  public partial class ProductBacklog : Page
  {
    ProductLogCollection productLogCollection = new ProductLogCollection();
    public ProductBacklog()
    {
      InitializeComponent();
    }

    public string getCounts()
    {
      return productLogCollection.Count().ToString();
    }
  }

SprintBacklog page

  public partial class SprintBackLog : Page
  {
    private ProductBacklog parent;


    public SprintBackLog(ProductBacklog parent)
    {
      InitializeComponent();
      this.parent = parent;

      textBlockError.Text = "Counts: " + parent.getCounts();
    }

I get this Error: XamlParseExeption occurred

No matching constructor found on type 'Projektstyring.SprintBackLog'. You can use the Arguments or FactoryMethod directives to construct this type.