Save XML asp.net

Hello

I have a webservice that receives an XmlDocument.

This file necessarily comes with the following information:

<nfeProc xmlns="http://www.portalfiscal.inf.br/nfe" versao="4.00">
<NFe xmlns="http://www.portalfiscal.inf.br/nfe">
    ...   
</NFe>  
</nfeProc>

I do not make any changes to the file, I only use the XmlDocumento.Save ("target_path"), however, when opening the saved file, it is in the following format:

<nfeProc xmlns="http://www.portalfiscal.inf.br/nfe" versao="4.00">  
<NFe>
    ...   </NFe> </nfeProc>

The file loses the NFe attribute information.

Does anyone know what it can be, please?