Do you mean when you debug in visual studio, it works fine? If so, it could about file rights. When you host the page on iis, the default user is the asp.net user, which would likely wouldn't have rights to a file path that you've show, certainly, not by default. It may be about giving windows file rights to the asp.net user so iis context user can access the file.
The .NET Framework is not specific to any one programming language; rather, it includes a library of functions that allows developers to rapidly build applications. Several supported languages include C#, VB.NET, C++ or ASP.NET.