using System;
using System.Xml;

namespace xmltest
{
 /// <summary>
 /// XmlTransoform 的摘要说明。
 /// </summary>
 public class XmlTransform
 {
  public XmlTransform()
  {
   
  }
  public ITagControl CreateControl(string nsuri,string tag,string innerxml)
  {
   return new SimpleTagControl(innerxml);
  }
  public string Transform(string xml,string nsuri)
  {
   System.IO.StringReader sr = new System.IO.StringReader(xml);
   XmlTextReader reader = new XmlTextReader(sr);
   System.IO.StringWriter sw = new System.IO.StringWriter();
   XmlTextWriter writer = new XmlTextWriter(sw);
   writer.Formatting=System.Xml.Formatting.Indented;
   reader.Read();
   while(!reader.EOF)
   {
    if(reader.NodeType==XmlNodeType.Element&&reader.NamespaceURI==nsuri)
    {
     string localname=reader.LocalName;
     ITagControl tc=CreateControl(nsuri,reader.LocalName,reader.ReadInnerXml());
     writer.WriteRaw(tc.Render());
     //     reader.Read(); reader.ReadInnerXml 已经进行的一次read
    }
    else
    {
     if(reader.NodeType==XmlNodeType.Element)
     {  
      bool isEmpty=false;
      if(reader.IsEmptyElement)
      {
       isEmpty=true;
      }
      writer.WriteStartElement(reader.Name);
      int count = reader.AttributeCount;
      for(int i=0;i<count;i++)
      {
       reader.MoveToAttribute(i);
       writer.WriteAttributeString(reader.Name,reader.Value);
      }
      if(isEmpty)
      {
       writer.WriteEndElement();
      }
      reader.Read();
     }
     else
     {     
      writer.WriteNode(reader,true);
     }
    }
   }
   return sw.ToString();
  }
 }
}
-------------------------------------------------

using System;
using System.Xml;

namespace xmltest
{
 /// <summary>
 /// SimpleTagControl 的摘要说明。
 /// </summary>
 public class SimpleTagControl: ITagControl
 {
 
  public SimpleTagControl()
  {
   
  }
 
  #region ITagControl 成员

  public string Render()
  {

   if(members==null||members.Count==0)
    return innerXml;
   else
   {
    System.IO.StringWriter w=new System.IO.StringWriter();
    XmlTextWriter xw=new XmlTextWriter(w);
    foreach(object key in members.Keys)
    {
     xw.WriteStartElement(key.ToString());
     xw.WriteString(members[key].ToString());
     xw.WriteEndElement();
    }
    return w.ToString();
   }
  }  
  protected string innerXml;
  public string InnerXml
  {
   get
   {
    return innerXml;
   }   
  }

  #endregion
 
  /// <input>innerXml</input>
  public SimpleTagControl(string innerXml)
  {
   init(innerXml);
  }
  private System.Collections.SortedList members;
  private void createMember(string key,string value)
  {
   if(members==null)
   {
    members=new System.Collections.SortedList();
   }
   if(members.ContainsKey(key))
   {
    members.Add(key,value);
   }
   else
   {
    members[key]=value;
   }
  }

  private void init(string innerXml)
  {
   this.innerXml=innerXml;
   if(innerXml.StartsWith("<"))
   {
    System.IO.StringReader sr = new System.IO.StringReader(innerXml);
    XmlTextReader reader = new XmlTextReader(sr);
    while(reader.Read())
    {
     if(reader.NodeType==XmlNodeType.Text)
     {
      return;
     }
     if(reader.NodeType==XmlNodeType.Element)
     {
      createMember(reader.LocalName,reader.ReadInnerXml());
     }
    }
   }
  }
 }
}
--------------------------------

[STAThread]
  static void Main(string[] args)
  {
   Class1 c1=new Class1();
   c1.transform();
   Console.ReadLine();  }
  public void transform()
  {
   string xml="<a xmlns:bb=\"http://ddd/\" xmlns:b='ss' key=\"keyname\"><bb:b a='c'><a>aaa</a></bb:b><a as='sdf'/><b:c key=\"dd\"><b xmlns=\"http://ddd1/\"><bb:h>hhh</bb:h></b></b:c><d>d1d1d1</d><e>eee</e></a>";
   XmlTransform st=new XmlTransform();
   Console.WriteLine(st.Transform(xml,@"http://ddd/"));   
  }

-----------------------------------------------------

欢迎就此问题进行评论，初步代码有待改进...

--fallseir.li 2005.4.23 0:36