如何删除声明并在现有XML文件（C＃）中添加根元素

Question

I'm fairly new to XML and C#, so please understand if this question is too sily to ask.

I'm converting XML format using C# win-form application. The app opens a xml file using OpenFileDialog , then conversion will be excuted(this is already done, but I still need to add or remove some more like below) . After conversion, the app will save the modified xml file using SaveFileDialog .

Original XML Format

<?xml version="1.0" encoding="utf-8" ?> 
   <DataList>
    <Data>
     <ID>1</ID>
     <Name>Mike</Name>
     <Age>23</Age>
    </Data> 
    <Data>
     <ID>1</ID>
     <Name>Mike</Name>
     <Age>23</Age>
    </Data>
    <Data>
     <ID>1</ID>
     <Name>Mike</Name>
     <Age>23</Age>
    </Data>
     ..<Data></Data> continued...
   </DataList>

I want to edit the XML file as below

<?xml version="1.0" encoding="utf-8" ?> **→ Remove this delaration!**
 <MainInterface> **→ Add 'root element' before existing nodes**
   <DataList>
    <Data>
     <ID>1</ID>
     <Name>Mike</Name>
     <Age>23</Age>
    </Data> 
    <Data>
     <ID>1</ID>
     <Name>Mike</Name>
     <Age>23</Age>
    </Data>
    <Data>
     <ID>1</ID>
     <Name>Mike</Name>
     <Age>23</Age>
    </Data>
     ..<Data></Data> continued...
   </DataList>
 </MainInterface> **→ close newly added root element**

I've tried below code but seem like it doesn't work

OpenFileDialog openFileDialogue = new OpenFileDialog();           
openFileDialog1.DefaultExt = "xml";
openFileDialog1.Filter = "xml files (*.xml)|*.xml";
openFileDialog1.Title = "Select a xml File";
openFileDialog1.ShowDialog();

XDocument xmlFile = XDocument.Load(openFileDialog1.FileName);
**// Remove Declaration**
XDocument doc = new XDocument(new XDeclaration(null, null, null));

**// Add Root Element**
XElement doc1 = XElement.Parse(openFileDialog1.FileName);
XElement root = new XElement("MainInterface", doc1);
//doc.Save(_data)
openFileDialog1.FileName = root.ToString();

-----------------------------------------------------------------------------------
Do something for conversion ~~~
-----------------------------------------------------------------------------------
SaveFileDialog saveFileDialogue1 = new SaveFileDialog();
saveFileDialog1.Filter = "xml File |*.xml";
saveFileDialog1.Title = "Conversion Completed! Save a XML file";
saveFileDialog1.FileName = "XML Converted.xml";            
saveFileDialog1.ShowDialog();
xmlFile.Save(saveFileDialog1.FileName);

The point is I'm not creating new XML file, but modifying existing xml file to get rid of declaration and add a root element. Should I use XML Writer? Is there simpler way of doing these? Thank you in advance.

Thank you for your answers. I found out this works for me!

SaveFileDialog saveFileDialogue1 = new SaveFileDialog();
saveFileDialog1.Filter = "xml File |*.xml";
saveFileDialog1.Title = "Conversion Completed! Save a XML file";
saveFileDialog1.FileName = "XML Converted.xml";            
saveFileDialog1.ShowDialog();

XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
StringWriter sw = new StringWriter();
using (XmlWriter xw = XmlWriter.Create(saveFileDialog1.FileName, settings))
   {
      xmlFile.Save(xw);
   }
string s = sw.ToString();

Answer 1

I would create a new XDocument , but just save it over the top of the old one:

// You don't want XElement.Parse here - that treats the filename as the
// XML itself!
XDocument oldDocument = XDocument.Load(openFileDialog1.FileName);
XDocument newDocument = new XDocument(new XElement("MainInterface", 
                                                   oldDocument.Root));
newDocument.Save(saveFileDialog1.FileName);

Answer 2

Create a new XmlDocument with only your root, then add the opened document to the first one excluding the Declaration:

foreach(XmlNode node in doc)
    if (node.NodeType != XmlNodeType.XmlDeclaration)
    {
// Add node logic here
    }

Write (or overwrite) with XmlWriter.

XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
settings.ConformanceLevel = ConformanceLevel.Fragment;