c# - Treeview IsExpanded not fires up -

i trying add treeview ability catch isexpanded event. when item expand raise property or command on view model.

here code:

  <treeview  name="scenariostreeview" itemssource="{binding path=cat, mode=twoway}" focusable="true" >      <treeview.inputbindings>        <keybinding key="delete" command="{binding deletecommand}" commandparameter="{binding selectedvalue ,elementname=scenariostreeview}" />      </treeview.inputbindings>       <treeview.itemcontainerstyle>        <style targettype="{x:type treeviewitem}">          <setter property="isexpanded" value="{binding isextended, mode=twoway}" />          <setter property="isselected" value="{binding isselected, mode=twoway}"/>        </style>      </treeview.itemcontainerstyle>       <treeview.resources>         <hierarchicaldatatemplate datatype="{x:type sotc:scenariocategory}" itemssource="{binding path=scenariolist}" >          <textblock  text="{binding path=name}" foreground="black" isenabled="true" focusable="true"/>        </hierarchicaldatatemplate>         <datatemplate datatype="{x:type sotc:scenario}" >          <textblock  text="{binding path=name, mode=twoway}" />        </datatemplate>      </treeview.resources>    </treeview> 

i have property in viewmodel isexpanded (and isselected) , none of raises when expand treeviewitem. ideas?

thanks ahead,

tried reproduce issue , implemented attached behavior calling command when node expanded , works fine. complete code solution:

xaml

<window x:class="treeviewtest.mainwindow"         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"         xmlns:sotc="clr-namespace:treeviewtest"         mc:ignorable="d"         title="mainwindow" height="350" width="525">     <window.datacontext>         <sotc:mainwindowviewmodel />     </window.datacontext>     <grid>         <treeview  name="scenariostreeview" itemssource="{binding path=cat, mode=twoway}" focusable="true" >             <treeview.inputbindings>                 <keybinding key="delete" command="{binding deletecommand}" commandparameter="{binding selectedvalue ,elementname=scenariostreeview}" />             </treeview.inputbindings>              <treeview.itemcontainerstyle>                 <style targettype="{x:type treeviewitem}">                     <setter property="isexpanded" value="{binding isextended, mode=twoway}" />                     <setter property="isselected" value="{binding isselected, mode=twoway}"/>                     <setter property="sotc:behaviours.expandingbehaviour" value="{binding datacontext.expandingcommand, relativesource={relativesource ancestortype=window}}"/>                 </style>             </treeview.itemcontainerstyle>              <treeview.resources>                 <hierarchicaldatatemplate datatype="{x:type sotc:scenariocategory}" itemssource="{binding path=scenariolist}" >                     <textblock  text="{binding path=name}" foreground="black" isenabled="true" focusable="true"/>                 </hierarchicaldatatemplate>                  <datatemplate datatype="{x:type sotc:scenario}" >                     <textblock  text="{binding path=name, mode=twoway}" />                 </datatemplate>             </treeview.resources>         </treeview>     </grid> </window> 

c#

public class viewmodelbase : inotifypropertychanged {      public void onpropertychanged([callermembername] string name = null)     {         propertychanged?.invoke(this, new propertychangedeventargs(name));     }      public event propertychangedeventhandler propertychanged; }  public class mainwindowviewmodel : viewmodelbase {     public icommand expandingcommand { get; set; }      private void executeexpandingcommand(object obj)     {         console.writeline(@"expanded");     }     private bool canexecuteexpandingcommand(object obj)     {         return true;     }      public mainwindowviewmodel()     {         expandingcommand = new relaycommand(executeexpandingcommand, canexecuteexpandingcommand);          cat = new observablecollection<scenariocategory>(new scenariocategory[]          {             new scenariocategory { name = "c1" }, new scenariocategory { name = "c2" }, new scenariocategory { name = "c3" }         });     }      public observablecollection<scenariocategory> cat { get; set; } }   public class scenariocategory : viewmodelbase {     string _name;     public string name     {         { return _name; }         set { _name = value; onpropertychanged(); }     }      bool _isextended;     public bool isextended     {         { return _isextended; }         set         {             _isextended = value;             console.writeline(@"isextended set");             onpropertychanged();         }     }      bool _isselected;     public bool isselected     {         { return _isselected; }         set         {             _isselected = value;             console.writeline(@"isselected set");             onpropertychanged();         }     }      public observablecollection<scenario> scenariolist { get; set; }      public scenariocategory()     {         scenariolist = new observablecollection<scenario>(new scenario[] { new scenario { name = "1" }, new scenario { name = "2" }, new scenario { name = "3" } });     }  }  public class scenario : viewmodelbase {     string _name;     public string name     {         { return _name; }         set { _name = value; onpropertychanged(); }     }      bool _isextended;     public bool isextended     {         { return _isextended; }         set         {             _isextended = value;             onpropertychanged();         }     }      bool _isselected;     public bool isselected     {         { return _isselected; }         set         {             _isselected = value;             onpropertychanged();         }     } }   public static class behaviours {     public static readonly dependencyproperty expandingbehaviourproperty =         dependencyproperty.registerattached("expandingbehaviour", typeof(icommand), typeof(behaviours),             new propertymetadata(onexpandingbehaviourchanged));       public static void setexpandingbehaviour(dependencyobject o, icommand value)     {         o.setvalue(expandingbehaviourproperty, value);     }     public static icommand getexpandingbehaviour(dependencyobject o)     {         return (icommand)o.getvalue(expandingbehaviourproperty);     }     private static void onexpandingbehaviourchanged(dependencyobject d, dependencypropertychangedeventargs e)     {         treeviewitem tvi = d treeviewitem;         if (tvi != null)         {             icommand ic = e.newvalue icommand;             if (ic != null)             {                 tvi.expanded += (s, a) =>                 {                     if (ic.canexecute(a))                     {                         ic.execute(a);                      }                     a.handled = true;                 };             }         }     } }   public class relaycommand : icommand {     private action<object> execute;     private func<object, bool> canexecute;      public event eventhandler canexecutechanged     {         add { commandmanager.requerysuggested += value; }         remove { commandmanager.requerysuggested -= value; }     }      public relaycommand(action<object> execute, func<object, bool> canexecute = null)     {         this.execute = execute;         this.canexecute = canexecute;     }      public bool canexecute(object parameter)     {         return this.canexecute == null || this.canexecute(parameter);     }      public void execute(object parameter)     {         this.execute(parameter);     } }