Code Behing update web.config mapping issue

Question

I from the code behind I need to update my web.config. This has never been a problem before, however I am getting an error recently. The errors say "Failed to map the path '/'." The lines commented out were different variations of what i tried.

//Configuration myWebConfig = WebConfigurationManager.OpenWebConfiguration(Server.MapPath("~"));
        //Configuration myWebConfig = WebConfigurationManager.OpenWebConfiguration("~");
        //Configuration myWebConfig = WebConfigurationManager.OpenWebConfiguration(null);
        Configuration myWebConfig = WebConfigurationManager.OpenWebConfiguration(".");
        // update pages theme
        RoleManagerSection section = (RoleManagerSection)myWebConfig.GetSection("system.web/roleManager");
        section.DefaultProvider = "SqlRoleManager";
        section.Providers.Clear();
        ProviderSettings providerSettings = new ProviderSettings();
        providerSettings.Name = "SqlRoleManager";
        providerSettings.Type = "System.Web.Security.SqlRoleProvider";
        providerSettings.Parameters.Clear();
        providerSettings.Parameters.Add("connectionStringName", "SimpleTickConnection");
        providerSettings.Parameters.Add("applicationName", "TheaterSales");
        section.Providers.Add(providerSettings);
        myWebConfig.Save();

Answer 1

I figured out the reason for the error. After moving the site from my local C: drive to a western digital passport and running the app the error started. The line of code below is fine:

Configuration myWebConfig = WebConfigurationManager.OpenWebConfiguration("~/");