windows phone 7 - How to Refresh Longlist Selector? -

this xaml code

<grid>                         <phone:longlistselector name="ilist"  itemssource="{binding}" grid.row="1">                             <phone:longlistselector.itemtemplate>                                 <datatemplate>                                      <stackpanel height="60">                                         <grid height="50">                                              <textblock                                                  grid.column="0"                                                 textwrapping="nowrap"                                                 text="{binding mail}"                                                 foreground="black"                                                 fontsize="25"                                                 margin="0,0,43,10"/>                                             <button  visibility="{binding btnvisible}"  margin="411,-16,-21,2" borderbrush="transparent" style="{staticresource buttonstyle1}">                                                 <button.background>                                                     <imagebrush  stretch="uniform" imagesource="/assets/icons/inviteplusicon.png"/>                                                 </button.background>                                             </button>                                             <checkbox content="checkbox"                                                    ischecked="{binding ischecked,mode=twoway}"                                                    visibility="{binding cbvisible}"                                                    background="skyblue"                                                    horizontalalignment="left"                                                    margin="400,-13,0,-4"                                                    verticalalignment="top" height="67" width="53"/>                                              <border borderbrush="#ffe0e0e0" borderthickness="0 0 0 1" horizontalalignment="left" width="456" />                                          </grid>                                      </stackpanel>                                 </datatemplate>                             </phone:longlistselector.itemtemplate>                         </phone:longlistselector>                      </grid> 

[1] when click edit application bar button. need page refresh , checkbox visible true , button visible false

[2]how refresh longlist selector?

[3]how change dynamic control display?

[4]check xaml code. correct or not?

[5]anyone hellp me?