Drag and Drop between two CustomContactList problem

hello i'm building small wpf app want drag , drop items between 2 customcontactlist.

i want when drag contact has moved list , not copied. , code don't permit me this. here sample of screenshot :

//event handler mouse down of listbox.  //this start drag drop operation private void mousedownhandler(object sender, mousebuttoneventargs e) { 	customcontactlist parent = (customcontactlist)sender;  	//set drag source can 	//remove item once item dropped on listbox 	firstlist = parent;  	//get object source selected item 	object data = getobjectdatafrompoint(parent, e.getposition(parent)); 	//if data not null start drag drop operation 	if (data != null) 			dragdrop.dodragdrop(parent, data, dragdropeffects.all); }    //event handler drop event of listbox private void drophandler(object sender, drageventargs e) {  	customcontactlist parent = (customcontactlist)sender; 	
	//get data arguments.    //we specify typeof string since know our data type 	object data = e.data.getdata(typeof(string));  	//remove object source. collection must implement inotifycollectionchanged 	//firstlist.removeat(0);  //<- here issue there no removeat in lync!!   	//add new parent (the "destination" listbox) 	parent.items.add(data); }  //gets object element selected (from point) in listbox (source) private static object getobjectdatafrompoint(customcontactlist source, point point) { 	uielement element = source.inputhittest(point) uielement;  	var frameworkelement = element frameworkelement; 	if (frameworkelement != null) 	{ 		//on récupère dans dc tout le datacontext qui contient les différentes informatioons 		if (frameworkelement.datacontext != null) 		{ 			var dc = frameworkelement.datacontext.tostring(); 			if (parsenuri(dc) != null) 			{ 				return parsenuri(dc); 			}     		} 		else 		{ 			return null; 		} 	} 	return null; } 
 //parse of datacontext have uri" private static object parsenuri (string str) { 	if (str.indexof("uri") != -1) 	{ 		char[] delimiterchars = { ':', '}' }; 		string[] words = str.split(delimiterchars);  		foreach (string s in words) 		{ 			if (s.indexof("+") != -1) 			{ 				return s; 			} 			else if (s.indexof("@") != -1) 			{ 				return s; 			} 			else 			{ 				continue; 			} 		} 	} 	return null; }

this xaml :

<!-- //////////////////////////////////////////// first contact list //////////////////////////////////////////// --> 
<controls:customcontactlist x:name="firstlist" horizontalalignment="left" height="256" margin="5,2.5,0,0" verticalalignment="top"                    width="390" background="#fff5ffd3"                   previewmouseleftbuttondown="mousedownhandler" grid.columnspan="4" grid.row="2"                   />   <!-- //////////////////////////////////////////// second contact list //////////////////////////////////////////// --> <controls:customcontactlist x:name="secondlist" horizontalalignment="center" height="136" margin="7,0,10,10" verticalalignment="bottom"                    width="492" rendertransformorigin="0.5,0.5"  background="#ffe3ffe3" grid.columnspan="3" grid.row="5"                   allowdrop="true" drop="drophandler" grid.column="2"                                               />

so please see huge mistake in code?  i inspired myself code make drag , drop.

so want delete item wich dragged , dropped first second list , apparently there no removeat working on customcontactlist...

i see i'm not manipulating customcontactlistitem during drag , drop operation maybe it's error. 

and because of can drag same contact first list , dropped thousand of times in other list... , need unique. if can move list resolve problem.

thank lot,

sincerely, ahmed ben salem

Lync Server  ,  Unified Communications  >  Microsoft Lync Client Development