How to Secure Web.Config File

Question

Hi,
The below is the connection string in Web.Config File.
<connectionStrings>
<add name="DBConnectionString" connectionString="Data Source=localhost;Initial Catalog=Master;User ID=sa;Password=t1234@asd" providerName="System.Data.SqlClient" />
We are Using Inproc Session:
<sessionState mode="InProc"
cookieless="false"
timeout="1440"/>
I need to Encrypt and Decrypt ConnectionString.
Example:
I seacrh in google ,
  So i tried with RSAProtectedConfigurationProvider.
 when i encrypt the file in web.config , the connectionstring is encrypted.
Configuration confg =WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);
ConfigurationSection configSect = confg.GetSection("connectionStrings");
if (configSect != null)
{
configSect.SectionInformation.ProtectSection("RSAProtectedConfigurationProvider");
confg.Save();
}
Above code is i copied in Login_Click Event , when the user gives username and pwd and click the button.
If successfull user redirecting to the page.
Response.Redirect("Sample.aspx");
It redirecting to Sample.aspx page , but the session null again redirecting to Home.aspx.
In Sample.aspx page:
public void Page_Load()
{
if (Session[USER_NAME] == null)
{
Response.Redirect( Home.aspx");
}
else
{
}
Why Session is Null? Can you please suggest me how to secure that connectionstring and users have to access my site without any problems.
Thanks,
Suresh