Remove duplicate data from XML using C# and VB.Net in ASP.Net

Hi friends how to remove duplicate data in xml? in c#

in below xml material code is duplicate so i need to remove that forecast details.. please Help

<rootnode> 
<ForecastDetails>
    <Year>2019</Year>
    <Month>04</Month>
    <Material_Code>1422346</Material_Code>
    <Position_Code>BL</Position_Code>
    <PeakSale>0</PeakSale>
    <AverageSale>0</AverageSale>
    <Apr>0</Apr>
    <May>0</May>
    <Jun>0</Jun>
    <Jul>0</Jul>
    <Aug>0</Aug>
    <Sep>0</Sep>
  </ForecastDetails>
  <ForecastDetails>
    <Year>2019</Year>
    <Month>04</Month>
    <Material_Code>1422346</Material_Code>
    <Position_Code>BL</Position_Code>
    <PeakSale>0</PeakSale>
    <AverageSale>0</AverageSale>
    <Apr>0</Apr>
    <May>0</May>
    <Jun>0</Jun>
    <Jul>0</Jul>
    <Aug>0</Aug>
    <Sep>0</Sep>
  </ForecastDetails>
</rootnode>

XDocument xDoc = XDocument.Parse(xml);
                xDoc.Root.Elements("test")
                         .SelectMany(s => s.Elements("ForecastDetails")
                                           .GroupBy(g => g.Attribute("Material_Code").Value)
                                           .SelectMany(m => m.Skip(1))).Remove();
                string testing = xDoc.ToString();