c# - WPF DataGrid: IsVirtualizingWhenGrouping="True" not working -

i have datagrid has collectionviewsource bound it's itemsource property:

<datagrid grid.row="0" rowbackground="#10808080" alternatingrowbackground="transparent"           horizontalalignment="stretch" verticalalignment="stretch"           itemssource="{binding source={staticresource bookingsviewsource}}"           rowheight="27"           virtualizingpanel.isvirtualizingwhengrouping="true"           virtualizingpanel.iscontainervirtualizable="true"           virtualizingpanel.scrollunit="item"           autogeneratecolumns="false">      <datagrid.columns>         <datagridtextcolumn binding="{binding date, stringformat=dd.mm.yyyy}" header="date"/>         <datagridtextcolumn binding="{binding path=customers.name}" header="customer"/>         <datagridtextcolumn binding="{binding path=customers.street}" header="adress"/>     </datagrid.columns>      <datagrid.groupstyle>         <groupstyle>             <groupstyle.containerstyle>                 <style targettype="{x:type groupitem}">                     <setter property="template">                         <setter.value>                             <controltemplate>                                 <expander header="{binding path=name}" isexpanded="true">                                     <itemspresenter />                                 </expander>                             </controltemplate>                         </setter.value>                     </setter>                 </style>             </groupstyle.containerstyle>         </groupstyle>     </datagrid.groupstyle> </datagrid> 

bookingsviewsource defined as

<collectionviewsource x:key="bookingsviewsource"                       d:designsource="{d:designinstance {x:type database:bookings}}">     <collectionviewsource.groupdescriptions>         <propertygroupdescription propertyname="providerid"/>     </collectionviewsource.groupdescriptions> </collectionviewsource> 

and get's filled in code behind section. doing fine fast , smooth without grouping. when added grouping <propertygroupdescription propertyname="providerid"/> datagrid needs around 1 minute load.

in .net 4.5 there new property called virtualizingpanel.isvirtualizingwhengrouping , set true loading time not decreasing.

i can not figure out why. ideas?

from book: macdonald m. - pro wpf 4.5 in c#

a number of factors can break ui virtualization, when don’t expect it:

• putting list control in scrollviewer: scrollviewer provides window onto child content. problem child content given unlimited “virtual” space. in virtual space, listbox renders @ full size, of child items on display. side effect, each item gets own memory-hogging listboxitem object. problem occurs time place listbox in container doesn’t attempt constrain size; example, same problem crops if pop stackpanel instead of grid.
• changing list’s control template , failing use itemspresenter: itemspresenter uses itemspaneltemplate, specifies virtualizingstackpanel. if break relationship or if change itemspaneltemplate doesn’t use virtualizingstackpanel, you’ll lose virtualization feature.
• not using data binding: should obvious, if fill list programmatically— example, dynamically creating listboxitem objects need—no virtualization occur. of course, can consider using own optimization strategy, such creating objects need , creating them @ time they’re needed. you’ll see technique in action treeview uses just-in-time node creation fill directory tree in chapter 22. if have large list, need avoid these practices ensure performance.

also, in case issue caused mahapps.metro styles.