title: adding items to a listbox from another wpf window
body: <p>so I have my MainWindow that contains a list box <code>menu_listbox</code> and a button <code>Add_menu_item</code> that when clicked will open a second wpf window <code>New_menu_item</code> in which I have texboxes and a button <code>Add_new_menu_item</code> 
  when the butoon is clicked it will close the <code>New_menu_item</code> window and add the values to the class <code>new_listbox_item</code> when I try and add a new item all the previous items are updated to new item added. the code  use is bellow</p>
  
  <pre><code>        private void add_menu_item_Click(object sender, RoutedEventArgs e)
      {
          new_menu_item form1 = new new_menu_item();
          form1.ShowDialog();
  
          new_listbox_item M_item = new new_listbox_item();
          M_item.new_item_name = form1.new_food.Text;
          M_item.price = double.Parse(form1.food_price.Text);
          M_item.vegitarian = form1.is_vegetarian.IsChecked == true;
          menu_Listbox.Items.Add(M_item);
      }
  </code></pre>
  
  <p>does anyone have any ideas on how to solve this issue?
  the <code>new_listbox_item</code> looks like this:</p>
  
  <pre><code>using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using System.Threading.Tasks;
  
  namespace MainServerWIndow
  {    
     public class new_listbox_item
     {
  
         private static string _item_name;
         private static Boolean _vegitarian;
         private static double _price;
         private static double _total;
         private double N_price;
  
  
         public string new_item_name
         {
             get
             {
                 return _item_name;
             }
             set
             {
                 _item_name = value;
             }
         }
  
          public Boolean vegitarian
         {
             get
             {
                 return _vegitarian;
             }
             set
             {
                 _vegitarian = value;
             }
         }
  
          public  double price
          {
              get
              {
                  return _price;
              }
              set
              {
                  _price = value;
              }
          }
  
          public static string item_name
          {
              get
              {
                  return _item_name;
              }
              set
              {
                  _item_name = value;
              }
          }
  
          public static double item_price
          {
              get
              {
                  return _price;
              }
              set
              {
                  _price = value;
              }
          }
  
          public static Boolean vegetarian
          {
              get
              {
                  return _vegitarian;
              }
              set
              {
                  _vegitarian = value;
              }
          }
  
  
          public static double total
          {
              get
              {
                  return _total;
              }
              set
              {
                  _total = value;
              }
          }
  
          public override string ToString()
          {
              return string.Format("{0} {1} {2}", new_item_name, vegitarian, price);
          }
     }
  } 
  </code></pre>