windows phone 8 - How to Delete Item from Observable collection in C# -

i working on windows phone app , want delete item listbox.

i using following code list numbers=new list();

 observablecollection<string> mycollection = new observablecollection<string>(numbers);         int indexperson = listbox1.selectedindex;         mycollection.removeat(indexperson);         var = (observablecollection<string>)listbox1.itemssource;         listbox1.itemssource=my; 

and when click on delete button 1 item deleted based on index , when delete item deleted item show , current deleted item deleted.

how can delete items?

if want clear items can use

mycollection.clearitems() 

if want remove selected item use

 mycollection.remove(listbox1.selecteditem)