如何在XDocument中放入Linq变量

我有以下代码，但它不起作用。我怎样才能做到这一点？下面的代码给出了一个示例：newXdoc.Add(cComb(此操作将创建结构不正确的文档

(还有给Gert Jan的thnx，他为我提供了部分代码(

private void button1_Click(object sender, EventArgs e)
{
    var x1 = XDocument.Load(sourceFilepathTb.Text);
    var x2 = XDocument.Load(targetFilepathTb.Text);
    // select the CLASS nodes from each
    var c1 = x1.Descendants("ActionDesign").First().Descendants("Action");
    var c2 = x2.Descendants("ActionDesign").First().Descendants("Action");
    // this one gives the distinct union of the two, you can 
    // put that into the result xdoc.
    var cComb =
        c1
        .Union(c2)
        .Distinct(new ClassComparer())
        .OrderBy(c => c.Attribute("Id").Value);
    XDocument newXdoc = new XDocument(
        new XDeclaration("1", "utf-8", null),
        new XElement("Application"));
    //newXdoc.Add(new XElement(cComb));
    //newXdoc.Add(new XDeclaration("1", "utf-8", "yes"));
    newXdoc.Add(cComb);

newXdoc.Root.Add(cComb);