This article will guide you how to resolve a virtualPath issue that may appear in SharePoint 2013 when trying to add a 3rd party library (for example SignalR), or when you use the “~” symbol in the path. We encountered this issue while developing a plugin that allows you to integrate the GroupDocs.Annotation for .NET library into SharePoint. Overall, the issue is quite strange, as it is not reported in the stack trace or logs.... Create a new class with the following code:...private static object \_lock = new object(); public void Init(HttpApplication...