We have an ASP.NET site that uses a plethora of Telerik controls – RadGrids, RadWindows, RadMenus, RadHamburgers – we have it all. In this case, our issue was with the RadTabStrip.
First off, it wasn’t a Telerik problem, it was an issue with our setup. We have Button controls that are global for the application, and six tabs to hold our various pages. Four of our six pages were working fine, but two of them were displaying this message when clicking on one of the application-wide buttons:
_visibilityMode is null or not an object
Cutting to the chase, the four tabs that worked had a RadWindowManager in each. So, I added one to the two tabs that were not working, and that did the trick:
<telerik:RadWindowManager ID=”RadWindowManager1″ ShowContentDuringLoad=”false” VisibleStatusbar=”false” ReloadOnShow=”true” runat=”server”>
<telerik:RadWindow ID=”myWindow” runat=”server” />