The fastest and easiest way to redirect http to https is to add this script below under the Application_BeginRequest section of your Global.asax file.

void Application_BeginRequest(object sender, EventArgs e)
{
if (!Request.IsSecureConnection)
{
string securePath = string.Format("https{0}", Request.Url.AbsoluteUri.Substring(4));
Response.Redirect(securePath);
}
}