Silverlight Invalid attribute value for property Visibility - silverlight

Question

In current project, i have to create a tab based navigation. Every time we click a module, a new TabControl opens if not alteady created, else focus. To achieve this i use a code like this:
HyperlinkButton link = (sender as HyperlinkButton);
string _name = "TAB_" + link.Name;
TabItem tabItem = (from TabItem item in TabControlID.Items
where item.Name.Equals(_name)
select item).FirstOrDefault();
if (tabItem == null)
{
tabItem = new TabItem();
tabItem.Header = link.Content;
tabItem.Name = _name;
tabItem.HorizontalAlignment = System.Windows.HorizontalAlignment.Stretch;
tabItem.VerticalAlignment = System.Windows.VerticalAlignment.Stretch;
switch (link.Name.ToString().ToLower())
{
case "taclass":
taClass_List taclass_list = new taClass_List();
tabItem.Content = taclass_list;
break;
}
TabControlID.Items.Add(tabItem);
tabItem.UpdateLayout();
TabControlID.UpdateLayout();
}
TabControlID.SelectedItem = tabItem;
This is working as expected, every tab has a UserControl associated (taClass_List in sample) where a grid with data is displayed. I have a few buttons to manage data: Add new record, Export to excel, Print data, Edit record and Delete record. The code for taClass_List is this
public partial class taClass_List : UserControl
{
private CespDomainContext _context = new CespDomainContext();
/// <summary>
///
/// </summary>
public taClass_List()
{
InitializeComponent();
LoadOperation<ta_Class> loadOp = this._context.Load(this._context.GetTa_ClassQuery());
MainGrid.ItemsSource = loadOp.Entities;
MainPager.Source = loadOp.Entities;
}
/// <summary>
/// s
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void saveChanges()
{
_context.SubmitChanges(OnSubmitCompleted, null);
}
/// <summary>
///
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void rejectChanges()
{
_context.RejectChanges();
CheckChanges();
}
/// <summary>
///
/// </summary>
private void CheckChanges()
{
EntityChangeSet changeSet = _context.EntityContainer.GetChanges();
bool hasChanges = _context.HasChanges;
}
/// <summary>
///
/// </summary>
/// <param name="so"></param>
private void OnSubmitCompleted(SubmitOperation so)
{
if (so.HasError)
{
MessageBox.Show(string.Format("Submit Failed: {0}", so.Error.Message));
so.MarkErrorAsHandled();
}
CheckChanges();
}
(...)
/// <summary>
///
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btAdd_Click(object sender, RoutedEventArgs e)
{
taClass_Form objform = new taClass_Form();
objform.IsTabStop = true;
objform.IsHitTestVisible = true;
objform.DataContext = _context;
objform.UpdateLayout();
objform.Closed += new EventHandler(objform_Closed);
objform.Show();
//MainPage.showWindow(objform);
}
/// <summary>
///
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void objform_Closed(object sender, EventArgs e)
{
taClass_Form objform = (taClass_Form)sender;
if (objform.MainObject != null)
{
//MainDataSource.DataView.Add(objform.MainObject);
//MainDataSource.SubmitChanges();
}
objform = null;
}
}
When i click Add New record button, btAdd_Click function is called, Childwindow appears but i receive an error message
Invalid attribute value for property Visibility
at MS.Internal.XcpImports.VisualStateManager_GoToState(Control reference, String StateName, Boolean useTransitions, Boolean& refreshInheritanceContext)
at System.Windows.VisualStateManager.GoToState(Control control, String stateName, Boolean useTransitions)
at System.Windows.Controls.ValidationSummary.UpdateCommonState(Boolean useTransitions)
at System.Windows.Controls.ValidationSummary.ValidationSummary_IsEnabledChanged(Object sender, DependencyPropertyChangedEventArgs e)
at System.Windows.Controls.Control.OnIsEnabledChanged(Control control, EventArgs args)
at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)
taClass_Form code is (so far):
public partial class taClass_Form : ChildWindow
{
public ta_Class MainObject = null;
public taClass_Form()
{
InitializeComponent();
}
private void OKButton_Click(object sender, RoutedEventArgs e)
{
this.DialogResult = true;
}
private void CancelButton_Click(object sender, RoutedEventArgs e)
{
this.DialogResult = false;
}
}
What am i doing wrong? Please help me
Thanks in advance.

Answer 1

After some more research, i discovered that problem is related with SilverLight Toolkit Themes.
I disabled theming in project and no more errors.
Thanks