c# - WPF Validation not working -

i created wpf serves serial number client. part of process, i'm trying validate length of each segment 5 characters long , of characters letters or numbers. followed outline given here.

the problem doesn't seem anything, , followed instructions submit button , submit incorrect data, whereas seems shouldn't validate if values aren't right. have binding path? if not, why won't fields validate?

the code validationrule looks this:

namespace syncagent.installer { class licensevalidationrule : validationrule {     public override validationresult validate(object value, cultureinfo cultureinfo)     {         if(!(value.tostring().length == 5))             return new validationresult(false,"incorrect number of characters.");          regex rexp = new regex("^[a-z0-9]*$");         if (!rexp.ismatch(value.tostring().toupper()))         {             return new validationresult(false,"a key may contain numbers , letters.");         }          return new validationresult(true, null);     } } } 

here's xaml:

<window x:name="wfusionkey" x:class="syncagent.installer.keyform"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:local="clr-namespace:syncagent.installer"     title="fusionkeyform" height="158" width="338" resizemode="noresize"> <grid margin="0,0,-6,1" horizontalalignment="left" width="334">     <grid.columndefinitions>         <columndefinition width="0*"/>         <columndefinition/>     </grid.columndefinitions>     <button x:name="btnokay" content="submit" horizontalalignment="left" margin="166,96,0,0" verticalalignment="top" width="75" grid.column="1" height="22" isdefault="true" click="btnokay_click"/>     <label x:name="lblfusionlicensekey" content="please enter 25-digit fusion license key here." horizontalalignment="left" margin="10,10,0,0" verticalalignment="top" grid.column="1" height="26" width="278"/>     <textbox x:name="txtfusion1" horizontalalignment="left" height="23" margin="10,57,0,0" textwrapping="wrap" verticalalignment="top" width="51" grid.column="1" maxlength="5" maxwidth="infinity">         <textbox.text>             <binding path="/" mode="default" updatesourcetrigger="propertychanged">                 <binding.validationrules>                     <local:licensevalidationrule/>                 </binding.validationrules>             </binding>         </textbox.text>     </textbox>     <button x:name="btncancel" grid.columnspan="2" content="cancel" horizontalalignment="left" margin="246,96,0,0" verticalalignment="top" width="75" iscancel="true"/>     <textbox x:name="txtfusion2" grid.columnspan="2" horizontalalignment="left" height="23" margin="76,57,0,0" textwrapping="wrap" verticalalignment="top" width="50" maxlength="5">         <textbox.text>             <binding path="left" updatesourcetrigger="propertychanged">                 <binding.validationrules>                     <local:licensevalidationrule/>                 </binding.validationrules>             </binding>         </textbox.text>     </textbox>     <textbox x:name="txtfusion3" grid.columnspan="2" horizontalalignment="left" height="23" margin="141,57,0,0" textwrapping="wrap" verticalalignment="top" width="50" maxlength="5">         <textbox.text>             <binding path="left" updatesourcetrigger="propertychanged">                 <binding.validationrules>                     <local:licensevalidationrule/>                 </binding.validationrules>             </binding>         </textbox.text>     </textbox>     <textbox x:name="txtfusion4" grid.columnspan="2" horizontalalignment="left" height="23" margin="206,57,0,0" textwrapping="wrap" verticalalignment="top" width="50" maxlength="5" rendertransformorigin="1.491,0.522">         <textbox.text>             <binding path="left" updatesourcetrigger="propertychanged">                 <binding.validationrules>                     <local:licensevalidationrule/>                 </binding.validationrules>             </binding>         </textbox.text>     </textbox>     <textbox x:name="txtfusion5" grid.columnspan="2" horizontalalignment="left" height="23" margin="271,57,0,0" textwrapping="wrap" verticalalignment="top" width="50" maxlength="5">         <textbox.text>             <binding path="left" updatesourcetrigger="propertychanged">                 <binding.validationrules>                     <local:licensevalidationrule/>                 </binding.validationrules>             </binding>         </textbox.text>     </textbox> 

i'm not sure textbox bound cannot see code behind, validator seems work ok when textbox text bound string.

here simple example of validator attached textbox bound string.

code:

/// <summary> /// interaction logic mainwindow.xaml /// </summary> public partial class mainwindow : window, inotifypropertychanged {     private string _mytexttovalidate;     public mainwindow()     {         initializecomponent();     }      public string mytexttovalidate     {         { return _mytexttovalidate; }         set { _mytexttovalidate = value; notifypropertychanged("mytexttovalidate"); }     }      public event propertychangedeventhandler propertychanged;     public void notifypropertychanged(string property)     {         if (propertychanged != null)         {             propertychanged(this, new propertychangedeventargs(property));         }     } } 

xaml:

<window x:class="wpfapplication11.mainwindow"         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         xmlns:local="clr-namespace:wpfapplication11"         title="mainwindow" height="89" width="166" name="ui">      <grid datacontext="{binding elementname=ui}">         <textbox height="23" margin="12" >             <textbox.text>                 <binding path="mytexttovalidate" updatesourcetrigger="propertychanged">                     <binding.validationrules>                         <local:licensevalidationrule/>                     </binding.validationrules>                 </binding>             </textbox.text>         </textbox>     </grid> </window> 

maybe track down issue.