wpf - DataGrid custom CanUserAddRows implementation -

i want implement custom add row button datagrid (it's long story). added button in template, , define attached property, , can button's click. can not add new row in generic way -not specified type-. know can similar thing in viewmodel, i'm looking in templates , attached properties. here try; idea complete this?

xaml:

<style x:key="{x:type datagrid}" targettype="{x:type datagrid}">     <setter property="template">         <setter.value>             <controltemplate targettype="{x:type datagrid}">                 <border x:name="border">                     <scrollviewer x:name="dg_scrollviewer" focusable="false">                         <scrollviewer.template>                             <controltemplate targettype="{x:type scrollviewer}">                                 <grid>                                     <grid.columndefinitions>                                         <columndefinition width="auto" />                                         <columndefinition width="*" />                                         <columndefinition width="auto" />                                     </grid.columndefinitions>                                     <grid.rowdefinitions>                                         <rowdefinition height="auto" />                                         <rowdefinition height="*" />                                         <rowdefinition height="auto" />                                     </grid.rowdefinitions>                                      <button focusable="false"                                             command="{x:static datagrid.selectallcommand}" />                                     <datagridcolumnheaderspresenter                                          x:name="part_columnheaderspresenter"                                         grid.column="1" />                                      <grid grid.columnspan="2" grid.row="1">                                         <grid.rowdefinitions>                                             <rowdefinition height="*"/>                                             <rowdefinition height="22" />                                         </grid.rowdefinitions>                                         <scrollcontentpresenter                                                  x:name="part_scrollcontentpresenter" />                                          <!-- custom button add new row -->                                         <button x:name="part_addrowbutton"                                                 content="add"/>                                     </grid>                                      <scrollbar x:name="part_verticalscrollbar"/>                                      <grid grid.column="1" grid.row="2">                                         <scrollbar x:name="part_horizontalscrollbar"/>                                     </grid>                                 </grid>                             </controltemplate>                         </scrollviewer.template>                         <itemspresenter snapstodevicepixels="{templatebinding snapstodevicepixels}" />                     </scrollviewer>                 </border>             </controltemplate>         </setter.value>     </setter> </style> 

c#:

public class datagridhelper {      public static readonly dependencyproperty canuseraddrowsproperty         = dependencyproperty.registerattached(         "canuseraddrows", typeof(bool), typeof(datagridhelper),         new frameworkpropertymetadata(default(bool), canuseraddrowschanged));      [attachedpropertybrowsablefortype(typeof(datagrid))]     public static bool getcanuseraddrows(dependencyobject obj) {         return (bool)obj.getvalue(canuseraddrowsproperty);     }      [attachedpropertybrowsablefortype(typeof(datagrid))]     public static void setcanuseraddrows(dependencyobject obj, bool value) {         obj.setvalue(canuseraddrowsproperty, value);     }      private static void canuseraddrowschanged(         dependencyobject d,         dependencypropertychangedeventargs e) {         var datagrid = d datagrid;         if (datagrid == null)             return;         bool oldvalue = (bool)e.oldvalue,             newvalue = (bool)e.newvalue;         if (newvalue == oldvalue)             return;         if (newvalue) {             datagrid.loaded += canuseraddrowsdatagridloaded;         } else {             datagrid.loaded -= canuseraddrowsdatagridloaded;         }     }      private static void canuseraddrowsdatagridloaded(object sender, routedeventargs e) {         var datagrid = sender datagrid;         if (datagrid == null)             return;         if (datagrid.style == null)             return;         var roottemplate = datagrid.template;         if (roottemplate == null)             return;         var scroll = roottemplate.findname("dg_scrollviewer", datagrid) scrollviewer;         if (scroll == null)             return;         var scrolltemplate = scroll.template;         if (scrolltemplate == null)             return;         var button = scrolltemplate.findname("part_addrowbutton", scroll) buttonbase;         if (button == null)             return;         if (getcanuseraddrows(datagrid)) {             button.click += addrowclicked;         } else {             button.click -= addrowclicked;         }     }      private static void addrowclicked(object sender, routedeventargs e) {         var button = ((buttonbase)sender);         var parent = visualtreehelper.getparent(button);         while (!(parent datagrid))             parent = visualtreehelper.getparent(parent);         var source = ((datagrid)parent).items.add(...) // what???     } } 

well, can see, got access datagrid after button got clicked; next? how can force datagrid show newitemplaceholder?

typically in wpf, bind collections (preferably collections support change notification observablecollection) of data objects ui controls. rather adding new items ui controls, add items collections in code behind/view model. long collection support change notification, ui controls automatically updated.

so add new row datagrid, need add new item collection:

datacollection.add(new datatype()); 

you should able access data bound collection in attachedproperty using:

var datacollection = (datacollectiontype)datagrid.itemssource; 

i believe can use:

datagrid.items.add(new datatype()); 

although method not recommended.