asp.net web app unable to locate config file

I have an ASP.NET Web Forms site. I am trying to get the HTTP Bindings from IIS8 programatically, but coming up with a problem. It is failing on the following line:

// Get the sites section from the AppPool.config 
        Microsoft.Web.Administration.ConfigurationSection sitesSection = Microsoft.Web.Administration.WebConfigurationManager.GetSection(null, null, "system.applicationHost/sites");

The error is:

The filename, directory name, or volume label syntax is incorrect. (Exception from HRESULT: 0x8007007B)

Interestingly, the following line identifies the correct web.config file. (I know the bindings aren't located in here, but I did this just to see if it can access other config files)

var configFile = AppDomain.CurrentDomain.SetupInformation.ConfigurationFile;

Does anyone know why this would be happening? Any advice will be appreciated! Thanks!