ASP.NET Web Configuration Tool and VS2013

Hello to everyone! I am trying to connect with Web Admin Tools doing exactly what is saying this article: http://stackoverflow.com/questions/20541680/visual-studio-2013-and-asp-net-web-configuration-tool but my browser throws the above error.

Server Error in '/WebAdmin' Application.

Compilation Error
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0122: 'System.Configuration.StringUtil' is inaccessible due to its protection level

Source Error:
Line 987:
Line 988: // Put together some unique app id
Line 989: string appId = StringUtil.GetNonRandomizedHashCode(String.Concat(appPath, appPhysPath)).ToString("x", CultureInfo.InvariantCulture);
Line 990:
Line 991:

Source File: c:\Windows\Microsoft.NET\Framework64\v4.0.30319\ASP.NETWebAdminFiles\App_Code\WebAdminPage.cs Line: 989

Any idea what happening?
Thank you!