c# - Inject controls in derived windows breaks xaml markup in combination with binding -

i trying inject layoutgrid , canvas windows, causes little headache:

here windowbase class:

public class windowbase : window {     protected override void oninitialized(eventargs e)     {         base.oninitialized(e);          if (content frameworkelement)         {             var originalcontent = content frameworkelement;             var grid = new grid();             grid.datacontext = originalcontent.datacontext;             content = grid;             grid.children.add(originalcontent);              var canvas = new canvas() { horizontalalignment = horizontalalignment.stretch, verticalalignment = verticalalignment.stretch };             grid.children.add(canvas);         }     } } 

my mainwindow thats inheriting windowbase looks this:

xaml:

<local:windowbase x:class="insertcanvastest.mainwindow"                   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"                   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"                   xmlns:local="clr-namespace:insertcanvastest"                   datacontext="{binding relativesource={relativesource self}}">     <border>         <grid>             <combobox selectedindex="1"                       itemssource="{binding itemsource1}" />         </grid>     </border> </local:windowbase> 

code behind of mainwindow:

public partial class mainwindow : windowbase {     private list<int> _itemsource1;     public list<int> itemsource1     {                 {             if (_itemsource1 == null)                 _itemsource1 = new list<int>(){1,2,3};             return _itemsource1;         }      }      public mainwindow()     {         initializecomponent();     } } 

as can see in xaml have specified selectedindex should 1, code in windowbase trying inject canvas , grid information gets lost , selectedindex @ -1.

is there way fix this?

i keep mainwindow window , not implement control , load different window inside contentpresenter of so.

i know problem wouldnt exist if declared canvas/grid in xaml directly instead of trying inject in codebehind, doing 100+ windows , trying maintain them if changes annoying.

change windowbase class :

windowbase

[contentproperty("internalcontent")] public class windowbase : window {     // internalcontent     public static readonly dependencyproperty internalcontentproperty =          dependencyproperty.register( "internalcontent", typeof(object),         typeof(windowbase), new frameworkpropertymetadata(null));      public object internalcontent     {         { return getvalue(internalcontentproperty); }         set { setvalue(internalcontentproperty, value); }     }      ... }  <window ...>     <grid>         ...         <contentcontrol istabstop="false"             content="{binding relativesource={relativesource mode=findancestor, ancestortype=window}, path=internalcontent}" />         <canvas />         ...     </grid> </window> 

in essence, create new internalcontent property subclasses see default content (thanks contentpropertyattribute), , display content contentcontrol.

that said, there better ways you're trying inheritance. using templates comes mind. or maybe adorners if want "above layer display things" canvas suggest.