Editor.aspx.cs

Uri uri = new Uri("http://" +
    Request.Url.Authority + "/Home/SaveTemplate");
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);

// get the AuthCookie
var authCookie =
    FormsAuthentication.GetAuthCookie(User.Identity.Name, true);

// create a new Cookie
Cookie requestAuthCoockie = new Cookie()
{
    Expires = authCookie.Expires,
    Name = authCookie.Name,
    Path = authCookie.Path,
    Secure = authCookie.Secure,
    Value = authCookie.Value,
    Domain = uri.Host,
    HttpOnly = authCookie.HttpOnly,
};

// add the AuthCookie to the WebRequest
request.CookieContainer = new CookieContainer();
request.CookieContainer.Add(requestAuthCoockie);