FormsAuthentication.GetRedirectUrl only get the first parameter of querystring

I found the issue with FormsAuthentication.GetRedirectUrl when it redirects then it redirects with the first querystring that you have while in fact you might have more than one querystring

e.g http://localhost/myweb/login.aspx?returnurl=myview.aspx?viewID=123&viewname=abc&viewall=false then the standard FormsAuthentication will redirect to http://localhost/myweb/myview.aspx?viewID=123

but where’s the remaining viewname querystring and viewall querystring??to fix this, just use the code below to pick the remaining querystring


  'this is used to fix the issue with FormsAuthentication.GetRedirectUrl only pick the first query string
            'get the original Redirect URL
            Dim redirectUrl As StringBuilder = New StringBuilder(FormsAuthentication.GetRedirectUrl(" ", True))
            Dim coll As NameValueCollection = objRequest.QueryString

            'iterate through every key in query string
            'add the missing query string
            For Each key As String In coll.AllKeys
                If (String.Compare(key, "returnurl", True)  0) Then
                    Dim values As String() = coll.GetValues(key)

                    If (values.Length > 0) Then
                        Dim pair As String = String.Format("{0}={1}", key, values(0))

                        If (redirectUrl.ToString().IndexOf(pair) < 0) Then
                            redirectUrl.Append("&" + pair)
                        End If
                    End If
                End If

            'this is to retain the original URL as in the query string