c# - Readonly DependencyProperty does not exist in XML namespace -

my existing c#/wpf project not working after installing visual studio 2008. working fine in visual studio 2008.

i'm getting following error on xaml

the property 'designtimehelper.designtimedata' not exist in xml namespace 'clr-namespace:monitor.controls'. line 13 position 5.

please find attached xaml , cs file

    <usercontrol         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"            xmlns:crl="clr-namespace:monitor.controls"         xmlns:dat="clr-namespace:system.windows.data;assembly=presentationframework"         xmlns:ui="clr-namespace:uicontrols;assembly=uicontrols"         crl:designtimehelper.designtimedata="{x:type svm:samplealertstabviewmodel}"         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:ignorable="d">          ...     </usercontrol> 

---

    using system;     using system.collections.generic;     using system.linq;     using system.text;     using system.componentmodel;     using system.windows;      namespace monitor.controls     {         public static class designtimehelper         {         public static readonly dependencyproperty designtimedataproperty =         dependencyproperty.registerattached("designtimedata", typeof(type), typeof(designtimehelper), new frameworkpropertymetadata(null, new propertychangedcallback(ondesigntimedatachanged)));          public static type getdesigntimedata(dependencyobject obj)         {             return (type)obj.getvalue(designtimedataproperty);         }          public static void setdesigntimedata(dependencyobject obj, type value)         {             obj.setvalue(designtimedataproperty, value);         }           private static void ondesigntimedatachanged(dependencyobject d, dependencypropertychangedeventargs e)         {             var isondesignmode = designerproperties.getisindesignmode(new dependencyobject());             if (isondesignmode)             {             var element = d frameworkelement;             if (element == null)                 throw new nullreferenceexception("element must not null , must uielement.");              var designtimedatatype = e.newvalue type;             if (designtimedatatype == null)                 throw new nullreferenceexception("designtimedatatype must not null.");              element.datacontext = activator.createinstance(designtimedatatype);             }         }         }     } 

why dependencyproperty not working ? requires other dependency?

please share ideas.

thanks