What is the correct way to overwrite the value of an XML element in c#.net?

Question

.NET

I want <fileOpen> </fileOpen>to change the value between, it doesn't work for some reason

XmlDocument doc = new XmlDocument();
                    doc.Load(GetFileName());
                    
                    //
                    //choose node for editing
                    XmlNode node = doc.SelectSingleNode($"/users/user[name={_PersonName} ]");    //node у меня null почемуто
                    XmlNode nodeFile = node.NextSibling;   //помогите
                    nodeFile = node.NextSibling;    
                    nodeFile.Value = openedFile;
                    doc.Save(GetFileName());

<users>
  <user>
    <name>dfg</name>
    <fileOpen>
    </fileOpen>
  </user>
</users>

Answer 1

doc.SelectSingleNode([email protected]"users/user[name=""{_PersonName}""]").LastChild.InnerText = openedFile;