这是同一个问题：
使用System.Xml.Linq命名空间显式元素关闭标记
但我使用Net 4.0，答案不再适用。
问题是我保存标签没有真正的值，我的输出XML看起来像这样：
<field/>
但我需要的是打开和关闭标签，即
<field></field>
题： 怎么做？
编辑
1
添加空节点：
if (field_xml == null) // always true, because I create the file for the first time
{
field_xml = new XElement(XMLKeys.field,String.Empty);
table_xml.Add(field_xml);
}
field_xml.SetAttributeValue(XMLKeys.name, field_info.Name);
// ... setting some other attributes of this node
然后，保存xml：
var writer = new FullEndingXmlTextWriter(parameters.OutputFilename, Encoding.UTF8);
root_xml.Save(writer);
FullEndingXmlTextWriter是Evil Greebo指出的专门类（它应该强制显式关闭标记）。
我无法重现你的错误。这在4.0和3.5 netFX中按预期工作：
namespace ExplicitXmlClosingTags
{
using System.Xml;
using System.Xml.Linq;
class Program
{
static void Main(string[] args)
{
const string ElementRoot = "RootElement";
const string ElementChild = "ChildElement";
const string AttributeChild = "ChildAttribute";
XDocument xDoc = new XDocument();
XElement root = new XElement(ElementRoot);
XElement child = new XElement(ElementChild, string.Empty);
root.Add(child);
child.SetAttributeValue(AttributeChild, "AttrValue");
xDoc.Add(root);
XmlWriterSettings xws = new XmlWriterSettings();
xws.Indent = true;
using (XmlWriter xw = XmlWriter.Create("out.xml", xws))
{
xDoc.Save(xw);
}
}
}
}
产生以下内容：
<?xml version="1.0" encoding="utf-8"?>
<RootElement>
<ChildElement ChildAttribute="AttrValue"></ChildElement>
</RootElement>
明确地设定 XElement 值为空字符串应该工作。 LINQ-to-XML已经处理了没有内容的节点（比如 new XElement("foo")）与内容长度为零的节点不同（如 new XElement("foo", string.Empty)），你可以从文档中看到 XElement.IsEmpty。
但是，如果不起作用，或者如果您需要微调XML输出的其他方面，您可以派生自定义 XmlWriter：
public class MyWriter : XmlWriter
{
private readonly XmlWriter inner;
public MyWriter(XmlWriter inner)
{
this.inner = inner;
}
public void Dispose()
{
((IDisposable) inner).Dispose();
}
public override void WriteStartDocument()
{
inner.WriteStartDocument();
}
public override void WriteStartDocument(bool standalone)
{
inner.WriteStartDocument(standalone);
}
public override void WriteEndDocument()
{
inner.WriteEndDocument();
}
public override void WriteDocType(string name, string pubid, string sysid, string subset)
{
inner.WriteDocType(name, pubid, sysid, subset);
}
public override void WriteStartElement(string prefix, string localName, string ns)
{
inner.WriteStartElement(prefix, localName, ns);
}
public override void WriteEndElement()
{
inner.WriteFullEndElement();
}
public override void WriteFullEndElement()
{
inner.WriteFullEndElement();
}
public override void WriteStartAttribute(string prefix, string localName, string ns)
{
inner.WriteStartAttribute(prefix, localName, ns);
}
public override void WriteEndAttribute()
{
inner.WriteEndAttribute();
}
public override void WriteCData(string text)
{
inner.WriteCData(text);
}
public override void WriteComment(string text)
{
inner.WriteComment(text);
}
public override void WriteProcessingInstruction(string name, string text)
{
inner.WriteProcessingInstruction(name, text);
}
public override void WriteEntityRef(string name)
{
inner.WriteEntityRef(name);
}
public override void WriteCharEntity(char ch)
{
inner.WriteCharEntity(ch);
}
public override void WriteWhitespace(string ws)
{
inner.WriteWhitespace(ws);
}
public override void WriteString(string text)
{
inner.WriteString(text);
}
public override void WriteSurrogateCharEntity(char lowChar, char highChar)
{
inner.WriteSurrogateCharEntity(lowChar, highChar);
}
public override void WriteChars(char[] buffer, int index, int count)
{
inner.WriteChars(buffer, index, count);
}
public override void WriteRaw(char[] buffer, int index, int count)
{
inner.WriteRaw(buffer, index, count);
}
public override void WriteRaw(string data)
{
inner.WriteRaw(data);
}
public override void WriteBase64(byte[] buffer, int index, int count)
{
inner.WriteBase64(buffer, index, count);
}
public override void Close()
{
inner.Close();
}
public override void Flush()
{
inner.Flush();
}
public override string LookupPrefix(string ns)
{
return inner.LookupPrefix(ns);
}
public override WriteState WriteState
{
get { return inner.WriteState; }
}
}
相关方法是这样的：
public override void WriteEndElement()
{
inner.WriteFullEndElement(); // always write both start and close tags
}
设置的值 XElement 至 String.Empty
要么
设置 IsEmpty 财产 false 对于没有任何子节点的所有元素
foreach (XElement childElement in
from x in document.DescendantNodes().OfType<XElement>()
where x.IsEmpty
select x)
{
childElement.IsEmpty = false;
}
var document = XDocument.Parse(XMLData);
foreach (XElement childElement in
from x in document.DescendantNodes().OfType<XElement>()
where x.IsEmpty
select x)
{
childElement.Value = "";
}
试试这个吧。只需更换 childElement.IsEmpty = false; 同 childElement.Value = "";