c# - Image not updating in WPF view -

i have created 1 wpf application , created flipview control in while rendering have used following code

<controls:flipview x:name="flipviewcontrol"                    itemssource="{binding product.images}"                    selectedindex="0"                    selectionchanged="flipviewcontrol_selectionchanged">     <controls:flipview.itemtemplate>         <datatemplate>             <image source="{binding}"                    stretch="fill" />         </datatemplate>     </controls:flipview.itemtemplate> </controls:flipview> 

the product.images observable collection of image uri's. when have changed product.images code behind view not updating.

private observablecollection<uri>  images;  public observablecollection<uri>  images {     { return images; }     set     {         images = value;         raisepropertychanged();     } }   public void setimages(ienumerable<uri> images)         {             images.clear();             foreach (var image in images)             {                 images.add(image);                 raisepropertychanged("product");             }         } 

it still shows first image.what reason?