How to access object between two control in silverlight

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C#

Silverlight

I have two control main page and child window..there is data grid on main page and on click of edit button of data grid i want to show row item in child window text box..
by using cw.textBox1=mainpage.selectitem its working but i want to used data binding with text box..so how to do it..i try and my code is...
MainPage.xaml.cs

namespace textbind
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
            CItem cv = dataGrid1.SelectedItem as CItem;
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {

        
            Service1Client proxy = new Service1Client();
            proxy.GetItemsCompleted +=new EventHandler<getitemscompletedeventargs>(proxy_GetItemsCompleted);
            proxy.GetItemsAsync();

        }
        void proxy_GetItemsCompleted(object sender, GetItemsCompletedEventArgs e)
        {
            dataGrid1.ItemsSource = e.Result;
        }
        
        private void btnEdit_Click(object sender, RoutedEventArgs e)
        {


            CItem ci = dataGrid1.SelectedItem as CItem;

            ChildWindow1 cw = new ChildWindow1();
            Person p = new Person();


            p.SName = "fdfdF";
         
            cw.Show();
        }
    }
}
</getitemscompletedeventargs>

ChildWindow.xaml.cs

namespace textbind
{
    public partial class ChildWindow1 : ChildWindow
    {
         private Person _model;

         public ChildWindow1()
      {
         InitializeComponent();
         MainPage m = new MainPage();
        CItem c=m.dataGrid1.SelectedItem as CItem;
       // string na = c.SADDRESS.ToString();
        Person person = new Person() { SName = null, SLocation = null };

        this.DataContext = person;
        person.SName = c.SNAME;
      }

      public Person Model
      {
         get { return _model; }
         set
         {
            if(value!=_model)
            {
               _model = value;
               DataContext = _model;
            }
         }
      }

      private void OKButton_Click(object sender, RoutedEventArgs e)
      {

      }

      private void CancelButton_Click(object sender, RoutedEventArgs e)
      {
          this.DialogResult = false;
      }
   }

   public class Person : INotifyPropertyChanged
   {
      private string _name;
      private string _location;
      public event PropertyChangedEventHandler PropertyChanged;

      public string SName
      {
         get { return _name; }
         set
         {
            if(value!=_name)
            {
               _name = value;
               RaisePropertyChanged("SName");
            }
         }
      }

      public string SLocation
      {
         get { return _location; }
         set
         {
            if (value != _location)
            {
               _location = value;
               RaisePropertyChanged("SLocation");
            }
         }
      }

      private void RaisePropertyChanged(string propertyName)
      {
         if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
      }
    }
}