Hi, We have design a application contains “XamOutlookBar” and we are adding “OutlookBarGroup” tabs dynamically with “XamTree” inside it. Now I am getting following error after “XamTreeItems” reloaded dynamically and click on other “OutlookBarGroup” Tab in “XamOutlookBar” control. Error: Unhandled Error in Silverlight Application Code: 4004 Category: ManagedRuntimeError Message: System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary. at System.ThrowHelper.ThrowKeyNotFoundException() at System.Collections.Generic.Dictionary`2.get_Item(TKey key) at System.Windows.ResourceManagerWrapper.GetResourceForUri(Uri xamlUri, Type componentType) Code: 0 URL: http://localhost:6722/InfragisticOutlookBarWithTreeTestPage.aspx PSA sample code, and follow the steps to reproduce the above error. 1. Run the application. 2. Select “Dashboard Manager” tab, 3. Click on “Design Dashboards” Refresh button to reload tree items. 4. Select any other outlookbargroup tab and then again select “Dashboard Manager” group tab. 5. It will gives the Unhandled Error. My requirement is to reload the tree items dynamically in xam tree by clicking on refresh button .