wpf - Bind to an element in the DataTemplate in DataGrid -

i have xaml below. not able bind chkextract checkbox chkheaderextract. want chkheaderextract ischecked="{binding elementname=chkextract" , on}. unable access chkextract name. unable access chkextract control anywhere in cs file. me how do binding.

<datagrid x:name="dgentities" frozencolumncount="13" isreadonly="true" maxwidth="854" height="444" canuseraddrows="false" selecteditem="{binding getselectedrow,mode=twoway,notifyontargetupdated=true}" itemssource="{binding jobentitiescollectionviewsource.view, mode=oneway, notifyontargetupdated=true}" autogeneratecolumns="false">                 <datagrid.columns>                     <datagridtextcolumn binding="{binding name}" header="entity" width="202" maxwidth="202" minwidth="202"/>                     <datagridtemplatecolumn header="status" width="138" maxwidth="138" minwidth="138">                         <datagridtemplatecolumn.celltemplate>                             <datatemplate>                                 <button margin="5" content="{binding extractstatus, mode=twoway, notifyontargetupdated=true}" command="{binding datacontext.hyperlinkcommand, relativesource={relativesource findancestor, ancestortype={x:type datagrid}}}" commandparameter="{binding selecteditem, elementname=dgentities}" cursor="hand" mousedoubleclick="control_onmousedoubleclick" >                                     <button.template>                                         <controltemplate targettype="{x:type button}">                                             <textblock style="{staticresource txtblkstyleextract}" textdecorations="none"><inlineuicontainer>                                                     <contentpresenter />                                                 </inlineuicontainer></textblock>                                         </controltemplate>                                     </button.template>                                 </button>                             </datatemplate>                         </datagridtemplatecolumn.celltemplate>                     </datagridtemplatecolumn>                      <datagridtemplatecolumn width="40" maxwidth="40" minwidth="40">                         <datagridtemplatecolumn.header>                              <checkbox x:name="chkheaderextract" width="26" command="{binding datacontext.headerextractcommand,relativesource={relativesource findancestor,ancestortype={x:type datagrid}},mode=oneway}" commandparameter="{binding ischecked,relativesource={relativesource self}}" ischecked="{binding datacontext.extractheadercheck,relativesource={relativesource findancestor,ancestortype={x:type datagrid}},mode=twoway}" />                          </datagridtemplatecolumn.header>                          <datagridtemplatecolumn.celltemplate>                              <datatemplate>                                  <checkbox  x:name="chkextract" horizontalalignment="center"  verticalalignment="center" command="{binding datacontext.individualextractcommand,relativesource={relativesource findancestor,ancestortype={x:type datagrid}},mode=oneway}" commandparameter="{binding ischecked,relativesource={relativesource self}}" ischecked="{binding extractisselected, mode=twoway, notifyontargetupdated=true, updatesourcetrigger=propertychanged}" />                              </datatemplate>                          </datagridtemplatecolumn.celltemplate>                      </datagridtemplatecolumn>  </datagrid.columns>             </datagrid> 

the problem chkextract inside of datatemplate, means has no knowledge of names outside of it.

this means items named within datatemplate can't seen in .cs file (code-behind)

the best way checkboxes affecting 1 via viewmodel; bind chkextract.ischecked properties of objects in collection grid uses, , bind header's chkheaderextract.ischecked property on datagrid's viewmodel. way, can control interaction using c# code in viewmodel.