Add new XElement with datatype attribute

Hi I have an xml file:

<?xml version="1.0"?>
<TreeList xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Columns>
    <Column>
      <ColumnName>123</ColumnName>
      <ColumnType>Bound</ColumnType>
    </Column>
  </Columns>
  <Nodes>
    <Node Id="0" ParentId="-1">
      <NodeData>
        <Cell xsi:type="xsd:string">Node1</Cell>
      </NodeData>
    </Node>
    <Node Id="1" ParentId="0">
      <NodeData>
        <Cell xsi:type="xsd:string">Node11</Cell>
      </NodeData>
    </Node>
  </Nodes>
</TreeList>

      

        
        
        
      

    

and I need to add a new XElement:

<Node Id="xx" ParentId="yy">
  <NodeData>
    <Cell xsi:type="xsd:string">NewNode</Cell>
  </NodeData>
</Node>

      

        
        
        
      

    

my problem is in the "xsi: type =" xsd: string "part of the XElement. How can I set the XAttribute like this?

I've tried the following:

    public static void AdNewNode(string filePath, string id, string parentId, string value)
    {
        XElement xml = XElement.Load(filePath);
        XNamespace xsi = "http://www.w3.org/2001/XMLSchema-instance";
        XNamespace xsd = "http://www.w3.org/2001/XMLSchema";
        XAttribute attribute1 = new XAttribute(xsd + "string", string.Empty);
        XAttribute attribute2 = new XAttribute(xsi + "type", attribute1.ToString());

        XElement innerNode = new XElement("NodeData", 
                        new XElement("Cell",attribute2, attribute1, value));
        XElement elemnet = new XElement("Node", new XAttribute("Id", id), new XAttribute("ParentId", parentId), innerNode);

        xml.Add(elemnet);
   }

      

        
        
        
      

    

And this is the result:

<Node Id="2" ParentId="1">
  <NodeData>
    <Cell p3:type="p0:string=&quot;&quot;" p4:string="" xmlns:p4="http://www.w3.org/2001/XMLSchema" xmlns:p3="http://www.w3.org/2001/XMLSchema-instance">New Node</Cell>
  </NodeData>
</Node> 

      

        
        
        
      

    

Can anyone help me?