wpf - Validation with IDataErrorInfo through DependencyProperty -

i've created small user control extend fun validation! problem validation not work: idataerrorinfo.this[] never called.

thank in advance help. stephan

here code:

<usercontrol x:class="wpfapplication5.textboxwithvalidation"          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"          x:name="textboxwithvalidationcontrol"> <grid>     <stackpanel orientation="horizontal">         <textbox height="23" width="120"                  text="{binding path=text,elementname=textboxwithvalidationcontrol, validatesondataerrors=true, updatesourcetrigger=propertychanged}">         </textbox>     </stackpanel> </grid> 

and code behind is:

public partial class textboxwithvalidation {     public static readonly dependencyproperty textproperty = dependencyproperty.register("text",                                                                                          typeof (object),                                                                                          typeof (                                                                                                  textboxwithvalidation                                                                                                  ),                                                                                          new frameworkpropertymetadata                                                                                                  (default(object),                                                                                                   frameworkpropertymetadataoptions                                                                                                           .bindstwowaybydefault));      public textboxwithvalidation()     {         initializecomponent();     }      public object text     {         { return getvalue(textproperty); }         set { setvalue(textproperty, value); }     } } 

now i'm using user control such:

<local:textboxwithvalidation text="{binding path=dummy.myproperty}" /> 

and dummy entity defined by:

public class dummy : inotifypropertychanged, idataerrorinfo {     private string _myproperty;      public string myproperty     {         { return _myproperty; }         set         {             _myproperty = value;             onpropertychanged("myproperty");         }     }      #region idataerrorinfo members      public string this[string columnname]     {         { return "this error"; }     }      public string error { get; private set; }      #endregion      #region inotifypropertychanged members      public event propertychangedeventhandler propertychanged;      #endregion      protected virtual void onpropertychanged(string propertyname)     {         propertychangedeventhandler handler = propertychanged;         if (handler != null)             handler(this, new propertychangedeventargs(propertyname));     } }