encrypting password in Web.config file

Question

I am trying with this command;

 

 

aspnet_regiis -pe "connectionStrings" -app "/wsMenupricing". (IN this folder is the Web.config file.)

To create the web.config with the encrypted passwords and usernames. But I et every time the message: 

A configuation file cannot be created for the requested Configuation Object.

 

Thanks.

 

Niels