Help needed. Button and Listbox "declared" in xaml is null in the code.

Hi all,
 
   I need some help. My btn2 and Listbox are null and I have no idea what went wrong.

xaml:

                    ChartTitle="Graph 1: 24-hour blood pressure pattern"
            YAxisTitle="Pressure (mmHg)"
            SecondaryYAxisTitle="Pulse Rate (beats/min)"
            DockPanel.Dock="Top"/>      
       .....
              
                        
                        
           
            
                       
            
               
       
   


and both BlockOne and BlockTwo are DependancyProperties:

public static DependencyProperty BlockOneProperties =            DependencyProperty.Register("BlockOne", typeof(List), typeof(Window1));

        public static DependencyProperty BlockTwoProperties =           DependencyProperty.Register("BlockTwo", typeof(List), typeof(Window1));

        public List BlockOne
        {
            get { return (List)GetValue(BlockOneProperties); }
            set { SetValue(BlockOneProperties, value); }
        }
         .....

and
BPClass have the following declaration:
 public class BPData : DependencyObject
    {   
        
        #region Public Property

        #region DateTimeProperty
        public static DependencyProperty DateTimeProperty =
            DependencyProperty.Register("DateTime", typeof(DateTime), typeof(BPData));

        public DateTime DateTime {
            get { return (DateTime)GetValue(DateTimeProperty) ;  }
            set { SetValue(DateTimeProperty, value); }
        }
        #endregion

        #region SystolicProperty
        public static DependencyProperty SystolicProperty =
                    DependencyProperty.Register("Systolic", typeof(int), typeof(BPData));

        public int Systolic {
            get { return (Int32)GetValue(SystolicProperty); }
            set { SetValue(SystolicProperty, value); }
        }
        #endregion
......



I am now stuck in a strange problem.
When I click on btn1, the Click action is triggered and the PlotChart method is called, a the listbox will be populated with the data.

but when I clicked on btn2, nothing happened, why isn't the  btn2_Click triggered (cos it null?? but why is it null when btn1 is worknig ) ?
 

Another issue is my BlockTwoDataTable is null in the PlotChart() method, whlist BlockOneDataTable is correctly reference to as a ListBox. Where did i go wrong?


I do a watch on this and was very shock to find the my btn2 and DataTableTwo is null.
:(

Thanks and Best Regards,
Zuff