wpf - In ListBox cannot add Items after ItemSource is set to null -

i have assigned itemssource property of first listbox 'listbox1' itemssource of listbox namely 'listbox2' . if set listbox2's itemssource null, unable add items further listbox1's itemssource.

below xaml snippet,

         <listbox verticalalignment="top" horizontalalignment="center" width="150" margin="0 25 0 0"                  x:name="listbox1" itemssource="{binding coll,mode=twoway}">             <listbox.itemtemplate>                 <datatemplate>                     <textblock text="{binding _name}"/>                 </datatemplate>             </listbox.itemtemplate>         </listbox>          <listbox verticalalignment="top" horizontalalignment="center" width="150" margin="0 25 0 0"                  x:name="listbox2" itemssource="{binding path=itemssource,elementname=listbox1,mode=twoway}">             <listbox.itemtemplate>                 <datatemplate>                     <textblock text="{binding _name}"/>                 </datatemplate>             </listbox.itemtemplate>         </listbox> 

in code behind, set itemsource of listbox2 null on button click below,

        listbox2.setcurrentvalue(listbox.itemssourceproperty, null); 

once done, tried add items listbox1's "coll" collection, throws nre "coll" null.

any suggestions plz.

regards, dinesh kumar p

the two-way binding on listbox2.itemssource sets listbox1.itemssource null when listbox2.itemssource set null. subsequently, two-way binding on listbox1.itemssource sets coll null.

don't make itemssource bindings two-way. not necessary, , collection changes still notified.

<listbox x:name="listbox1"          itemssource="{binding coll}" ... >     ... </listbox> <listbox x:name="listbox2"          itemssource="{binding path=itemssource, elementname=listbox1}" ... >     ... </listbox> 

it's not clear going achieve, may better bind listbox2.itemssource directly coll property.