I Try To Encrypt App.Config By Command Prompt But I Have Problem

See more:

C#

I try to encrypt app.config by command prompt
My Problem

This Is My code :
aspnet_regiis.exe -pef "connectionStrings" "C:\Users\Public\Documents\app.config"

The configuration for physical path '\C:\Users\Public\Documents\app.config'
cannot be opened.
Failed!