https://learn.microsoft.com/en-us/dotnet/api/system.web.hosting.virtualpathprovider.combinevirtualpaths?view=netframework-4.8.1
VirtualPathProvider.CombineVirtualPaths(String, String) Method (System.Web.Hosting) | Microsoft...
Combines a base path with a relative path to return a complete path to a virtual resource.
system webstringmethodhostingmicrosoft