自定义xmlWriter跳过某些元素？ [英] Custom xmlWriter to skip a certain element?
问题描述
我正在实现自定义xmlwriter，我想省略任何具有特定名称的元素，例如< ABC> 。
I am implementing a custom xmlwriter and I want to omit any elements with a particular name, like <ABC>.
实际上我该怎么做？我觉得我可能需要像这样覆盖 WriteStartElement 方法：
How do I actually do that? I get a sense that I might need to overwrite the WriteStartElement method like this:
public override void WriteStartElement(string prefix, string localName, string ns)
{
if (localName.Equals("ABC"))
{
return;
}
base.WriteStartElement(prefix, localName, ns);
}
我还需要覆盖 WriteEndElement 方法？如何告诉 WriteEndElement 方法跳过写结尾的< / ABC> 标记？我可以检查的 WriteEndElement 方法中似乎没有对 localName 的引用。？
Do I also need to overwrite WriteEndElement method? How do I tell WriteEndElement method to skip writing the end </ABC> tag? There seems to be no reference of the localName in WriteEndElement method that I can check...?
推荐答案
在我之前编写的一些示例代码中找到了这一点。它维护一个下推堆栈，以确定是否要写入元素结尾，这是您需要做的：
Found this in some sample code I wrote previously. It maintains a push-down stack to determine whether to write the element end, which is what you would need to do:
public class ElementSkippingXmlTextWriter : XmlWriterProxy
{
readonly Stack<bool> stack = new Stack<bool>();
readonly Func<string, string, int, bool> filter;
readonly Func<string, string, int, string> nameEditor;
readonly bool filterChildren;
public ElementSkippingXmlTextWriter(XmlWriter writer, Func<string, string, int, bool> filter, bool filterChildren)
: this(writer, filter, null, filterChildren)
{
}
public ElementSkippingXmlTextWriter(XmlWriter writer, Func<string, string, int, bool> filter, Func<string, string, int, string> nameEditor, bool filterChildren)
: base(writer)
{
this.filter = filter ?? delegate { return true; };
this.nameEditor = nameEditor ?? delegate(string localName, string ns, int depth) { return localName; };
this.filterChildren = filterChildren;
}
protected override bool IsSuspended
{
get
{
if (filterChildren)
{
if (!stack.All(b => b))
return true;
}
else
{
if (stack.Count > 0 && !stack.Peek())
return true;
}
return base.IsSuspended;
}
}
public override void WriteStartElement(string prefix, string localName, string ns)
{
var write = filter(localName, ns, stack.Count);
var newLocalName = nameEditor(localName, ns, stack.Count);
if (write)
base.WriteStartElement(prefix, newLocalName, ns);
stack.Push(write);
}
public override void WriteEndElement()
{
if (stack.Pop())
base.WriteEndElement();
}
}
public class XmlWriterProxy : XmlWriter
{
readonly XmlWriter baseWriter;
public XmlWriterProxy(XmlWriter baseWriter)
{
if (baseWriter == null)
throw new ArgumentNullException();
this.baseWriter = baseWriter;
}
protected virtual bool IsSuspended { get { return false; } }
public override void Close()
{
baseWriter.Close();
}
public override void Flush()
{
baseWriter.Flush();
}
public override string LookupPrefix(string ns)
{
return baseWriter.LookupPrefix(ns);
}
public override void WriteBase64(byte[] buffer, int index, int count)
{
if (IsSuspended)
return;
baseWriter.WriteBase64(buffer, index, count);
}
public override void WriteCData(string text)
{
if (IsSuspended)
return;
baseWriter.WriteCData(text);
}
public override void WriteCharEntity(char ch)
{
if (IsSuspended)
return;
baseWriter.WriteCharEntity(ch);
}
public override void WriteChars(char[] buffer, int index, int count)
{
if (IsSuspended)
return;
baseWriter.WriteChars(buffer, index, count);
}
public override void WriteComment(string text)
{
if (IsSuspended)
return;
baseWriter.WriteComment(text);
}
public override void WriteDocType(string name, string pubid, string sysid, string subset)
{
if (IsSuspended)
return;
baseWriter.WriteDocType(name, pubid, sysid, subset);
}
public override void WriteEndAttribute()
{
if (IsSuspended)
return;
baseWriter.WriteEndAttribute();
}
public override void WriteEndDocument()
{
if (IsSuspended)
return;
baseWriter.WriteEndDocument();
}
public override void WriteEndElement()
{
if (IsSuspended)
return;
baseWriter.WriteEndElement();
}
public override void WriteEntityRef(string name)
{
if (IsSuspended)
return;
baseWriter.WriteEntityRef(name);
}
public override void WriteFullEndElement()
{
if (IsSuspended)
return;
baseWriter.WriteFullEndElement();
}
public override void WriteProcessingInstruction(string name, string text)
{
if (IsSuspended)
return;
baseWriter.WriteProcessingInstruction(name, text);
}
public override void WriteRaw(string data)
{
if (IsSuspended)
return;
baseWriter.WriteRaw(data);
}
public override void WriteRaw(char[] buffer, int index, int count)
{
if (IsSuspended)
return;
baseWriter.WriteRaw(buffer, index, count);
}
public override void WriteStartAttribute(string prefix, string localName, string ns)
{
if (IsSuspended)
return;
baseWriter.WriteStartAttribute(prefix, localName, ns);
}
public override void WriteStartDocument(bool standalone)
{
baseWriter.WriteStartDocument(standalone);
}
public override void WriteStartDocument()
{
baseWriter.WriteStartDocument();
}
public override void WriteStartElement(string prefix, string localName, string ns)
{
if (IsSuspended)
return;
baseWriter.WriteStartElement(prefix, localName, ns);
}
public override WriteState WriteState
{
get { return baseWriter.WriteState; }
}
public override void WriteString(string text)
{
if (IsSuspended)
return;
baseWriter.WriteString(text);
}
public override void WriteSurrogateCharEntity(char lowChar, char highChar)
{
if (IsSuspended)
return;
baseWriter.WriteSurrogateCharEntity(lowChar, highChar);
}
public override void WriteWhitespace(string ws)
{
if (IsSuspended)
return;
baseWriter.WriteWhitespace(ws);
}
}
它包装了 XmlWriter ，您将像往常一样通过调用 XmlWriter.Create（） ，并过滤<$ c对应的元素（以及子元素） $ c> filter 委托返回 false 。
It wraps an XmlWriter you would create as usual with a call to XmlWriter.Create(), and filters elements (and, optionally, children) for which the filter delegate returns false.
注意-未经全面测试。 异步方法也可能需要被覆盖。
Note -- not fully tested. Async methods may need to be overridden as well.
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