wpf - scrollviewer the property 'content' is set more than once -

here code:

<grid style="{staticresource layoutrootstyle}">     <grid.rowdefinitions>         <rowdefinition height="140"/>         <rowdefinition height="*"/>     </grid.rowdefinitions>      <scrollviewer              grid.rowspan="2" style="{staticresource horizontalscrollviewerstyle}"             horizontalscrollbarvisibility="visible" >             <!-- elements want horizontally scrollable goes here -->             <!-- horizontal scrolling grid used in view states -->          <gridview             name="itemgridview"             automationproperties.automationid="itemsgridview"             automationproperties.name="items"             tabindex="1"             padding="100,136,116,46"             itemssource="{binding source={staticresource itemsviewsource}}"             itemtemplate="{staticresource standard250x250itemtemplate}"             selectionmode="none"             isswipeenabled="false"             isitemclickenabled="true"             itemclick="itemview_itemclick"/>           <button hello />  <!-- here come error -->                </scrollviewer> </grid> 

when add thing after gridview, give me error (the property content set more once).

the answer right there in error message. scrollviewer can have 1 child (you have two, gridview , button). if want add multiple things, have wrap them in panel allows multiple children (e.g. grid).