我的 XDeclaration 在哪里？

由于某种原因，以下代码生成不包含声明的 XML：

        XDocument xDocument = new XDocument(new XDeclaration("1.0", "utf-8", "yes"),
            new XElement("project",
                new XAttribute("number", project.ProjectNumber),
                new XElement("store",
                    new XAttribute("number", project.StoreNumber)
                ),

                // User Element
                new XElement("user", 
                    new XAttribute("owner-id", project.OwnerID ?? 0),
                    new XElement("email", new XCData(project.OwnerEmail ?? "")),
                    new XElement("project-name", new XCData(project.ProjectName ?? ""))
                ),

                // Nested Project Element
                new XElement("nested-project", 
                    new XAttribute("version", new Version(1, 0)),
                    new XElement("project", 
                        new XAttribute("version", new Version(1, 0)),
                        xProjectItems = new XElement("project-items")
                    ),
                    new XElement("price-per-part", project.PricePerPart),
                    new XElement("sheet-quantity", project.SheetQuantity),
                    new XElement("edge-length", project.EdgeLength),
                    new XElement("price", project.Price),
                    new XElement("status", project.Status),
                    xMaterialItems = new XElement("alternative-material-items"),
                    xProductItems = new XElement("project-product-items")
                )
            )
        );

        String strXML = xDocument.ToString();

它之前已经发表过声明。我错过了一些明显的东西吗？

Thanks.

当您使用其中之一时，XDeclaration 将可用XDocument.Save methods http://msdn.microsoft.com/en-us/library/system.xml.linq.xdocument.save.aspx。例如：

var doc = new XDocument (
            new XDeclaration ("1.0", "utf-8", "yes"),
            new XElement ("test", "data")
        );

string path = Path.Combine(Path.GetTempPath(), "temp.xml");
doc.Save(path);
Console.WriteLine(File.ReadAllText(path));

或者，您可以使用这种方法：

var sw = new StringWriter();
doc.Save(sw);
string result = sw.GetStringBuilder().ToString();
Console.WriteLine(result);

EDIT:请注意，某些方法会将 utf-8 名称转换为 utf-16。如果你想强制它是 utf-8，你将不得不使用这种不同的方法：

using (var mem = new MemoryStream())  
using (var writer = new XmlTextWriter(mem, System.Text.Encoding.UTF8))
{
    writer.Formatting = Formatting.Indented;
    doc.WriteTo(writer);
    writer.Flush();
    mem.Flush();
    mem.Seek(0, SeekOrigin.Begin);
    using (var reader = new StreamReader(mem))
    {
        var xml = reader.ReadToEnd();
        Console.WriteLine(xml);
    }
}