如何强制使用Linq XML显式标记关闭？

Question

这是相同的问题： Explicit Element Closing Tags with System.Xml.Linq Namespace

但我使用Net 4.0和答案不再工作。

问题是我保存的标签，没有价值真的，我的输出XML是这样的：

<field/>

但我需要的是始终在打开和关闭标签，即

<field></field>

问题：怎么办？

编辑

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 

后来，保存XML：

var writer = new FullEndingXmlTextWriter(parameters.OutputFilename, Encoding.UTF8); 
root_xml.Save(writer); 

FullEndingXmlTextWriter是专业类的邪恶Greebo指出（它应该强制显式结束标记）。

Answer 1

我无法重现您的错误。这将按预期在这两个4.0和3.5 NETFX：

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> 

Answer 2

设定的值XElement到String.Empty

OR

设置IsEmpty属性false不具有任何的子节点

foreach (XElement childElement in 
     from x in document.DescendantNodes().OfType<XElement>() 
     where x.IsEmpty 
     select x) 
    { 
     childElement.IsEmpty = false; 
    } 

Answer 3

的XElement值明确设置为空的所有元素字符串应该工作。正如您从XElement.IsEmpty的文档中看到的，LINQ到XML已经将节点没有内容（如new XElement("foo")）视为与长度为零的节点（如new XElement("foo", string.Empty)）不同。

但在不工作的情况下，或者如果你需要微调XML输出的一些其他方面，你可以得到一个定制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; } 
    } 
} 

相关的方法是这样的一种：

public override void WriteEndElement() 
{ 
    inner.WriteFullEndElement(); // always write both start and close tags 
} 

Answer 4

var document = XDocument.Parse(XMLData); 
         foreach (XElement childElement in 
         from x in document.DescendantNodes().OfType<XElement>() 
         where x.IsEmpty 
         select x) 
         { 
          childElement.Value = ""; 
         } 

试试这个工作。只需将childElement.IsEmpty = false;替换为childElement.Value = "";