SqlClient/doc/samples/ConnectionStringsWeb_Encrypt.cs

using System;
using System.Configuration;
using System.Web.Configuration;

class Program
{
    static void Main()
    {
    }
    // <Snippet1>
    static void ToggleWebEncrypt()
    {
        // Open the Web.config file.
        Configuration config = WebConfigurationManager.
            OpenWebConfiguration("~");

        // Get the connectionStrings section.
        ConnectionStringsSection section =
            config.GetSection("connectionStrings")
            as ConnectionStringsSection;

        // Toggle encryption.
        if (section.SectionInformation.IsProtected)
        {
            section.SectionInformation.UnprotectSection();
        }
        else
        {
            section.SectionInformation.ProtectSection(
                "DataProtectionConfigurationProvider");
        }

        // Save changes to the Web.config file.
        config.Save();
    }
    // </Snippet1>
}