c# - No defaultview of datagrid -

i want filter data that's loaded in datagrid. datagrid bounded entity of ef. read different posts on internet filtering , posts create code below. problem still can't want to. exception thrown because "mydata" null. why doesn't defaultview return data?

this xaml

<grid name="gg" datacontext="{staticresource t_klantenviewsource}">     <datagrid autogeneratecolumns="false" enablerowvirtualization="true" itemssource="{binding}" name="t_klantendatagrid" rowdetailsvisibilitymode="visiblewhenselected" isreadonly="true" canuserreordercolumns="false" canuserdeleterows="false" canuseraddrows="false" canuserresizerows="false" mousedoubleclick="t_klantendatagrid_mousedoubleclick" margin="0,21,0,10" fontsize="13">      </datagrid>     <textbox height="23" horizontalalignment="right" name="tbsearch" verticalalignment="top" width="120" margin="0,-7,99.2,0" textchanged="tbsearch_textchanged" /> </grid> 

this code

collectionviewsource t_klantenviewsource = ((system.windows.data.collectionviewsource)(this.findresource("t_klantenviewsource")));         system.data.objects.objectquery<aov.t_klanten> customersquery = this.getlt_klantenquery(aovent);         t_klantenviewsource.source = customersquery.execute(system.data.objects.mergeoption.appendonly);  private system.componentmodel.icollectionview mydata; string searchtext = string.empty;      private void tbsearch_textchanged(object sender, textchangedeventargs e)     {         mydata = collectionviewsource.getdefaultview(t_klantendatagrid.datacontext);         textbox t = sender textbox;         searchtext = t.text.tostring();         mydata.filter = filterdata;     } 

you need change first line mentioned in below updated code. getdefaultview accepts binding source.

 private void tbsearch_textchanged(object sender, textchangedeventargs e)         {             mydata = collectionviewsource.getdefaultview(t_klantendatagrid.itemssource);             textbox t = sender textbox;             searchtext = t.text.tostring();             mydata.filter = filterdata;         }