274 lines
9.5 KiB
C#
274 lines
9.5 KiB
C#
using HtmlAgilityPack;
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using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Linq;
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using System.Text;
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using System.Text.RegularExpressions;
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using System.Threading.Tasks;
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using System.Xml;
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namespace XSSAttacksFilter
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{
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public class HtmlFilter
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{
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#region 构造
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public HtmlFilter() : this(FilterPolicy.GetInstance()) { }
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public HtmlFilter(FileInfo FilterPolicyFile) : this(FilterPolicy.GetInstance(FilterPolicyFile)) { }
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public HtmlFilter(string FilterPolicyFilePath) : this(FilterPolicy.GetInstance(FilterPolicyFilePath)) { }
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public HtmlFilter(FilterPolicy policy)
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{
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if (policy == null)
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{
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throw new Exception();
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}
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Policy = policy;
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}
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#endregion
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#region 属性
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public FilterPolicy Policy { get; private set; }
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CssFilter _cssFilter;
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public CssFilter CssFilter
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{
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get
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{
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if (_cssFilter == null) { _cssFilter = new CssFilter(Policy); }
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return _cssFilter;
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}
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}
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#endregion
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#region 公共方法
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public virtual string Filters(string html)
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{
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if (html == null || html.Length == 0)
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{
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return string.Empty;
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}
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//had problems with the getting double encoded, so this converts it to a literal space.
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//this may need to be changed.
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html = html.Replace(" ", char.Parse("\u00a0").ToString());
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//We have to replace any invalid XML characters
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html = StripNonValidXMLCharacters(html);
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int maxInputSize = Policy.Directive<int>("maxInputSize");
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//ensure our input is less than the max
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if (maxInputSize > 0 && maxInputSize < html.Length)
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{
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return string.Empty;
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}
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//修复一些敏感标签
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if (!HtmlNode.ElementsFlags.Contains("iframe"))
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HtmlNode.ElementsFlags.Add("iframe", HtmlElementFlag.Empty);
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HtmlNode.ElementsFlags.Remove("form");
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HtmlDocument doc = new HtmlDocument();
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doc.LoadHtml(html);
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//设置自动添加结束标签
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doc.OptionAutoCloseOnEnd = true;
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//设置强制执行XML规则
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doc.OptionOutputAsXml = true;
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FiltersTags(doc.DocumentNode.ChildNodes);
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return doc.DocumentNode.InnerHtml;
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}
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#endregion
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#region 帮助方法
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/// <summary>
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/// 过滤标签集合
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/// </summary>
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/// <param name="nodes"></param>
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void FiltersTags(HtmlNodeCollection nodes)
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{
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for (int i = 0; i < nodes.Count; i++)
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{
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HtmlNode tmp = nodes[i];
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FiltesTag(tmp);
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if (tmp.ParentNode == null)
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{
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i--;
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}
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}
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}
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/// <summary>
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/// 过滤指定编辑器的属性和子元素
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/// </summary>
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/// <param name="node"></param>
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void FiltesTag(HtmlNode node)
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{
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string tagName = node.Name.ToLower();
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if (tagName.Equals("#text")) return;
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var tag = Policy.Tag(tagName);
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PolicyHtmlTagAction actoin = tag == null ? PolicyHtmlTagAction.Filter : tag.Action;
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switch (actoin)
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{
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case PolicyHtmlTagAction.Filter:
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///删除当前节点，但保留其有效的子节点
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PromoteChildren(node);
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return;
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case PolicyHtmlTagAction.Validate:
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///过滤当前元素的属性与及子节点
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ValidateAction(node, tagName, tag);
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return;
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case PolicyHtmlTagAction.Truncate:
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///删除当前节点的所有属性以及子节点，但保留文本和备注节点。
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TruncateAction(node);
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return;
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default:
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///将当前节点从父节点中删除。
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HtmlNode parentNode = node.ParentNode;
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parentNode.RemoveChild(node);
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break;
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}
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}
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void ValidateAction(HtmlNode node,string tagName,PolicyHtmlTag tag)
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{
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HtmlNode parentNode = node.ParentNode;
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#region 过滤样式
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if ("style".Equals(tagName))
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{
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try
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{
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node.FirstChild.InnerHtml = CssFilter.Filters(node.FirstChild.InnerHtml);
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}
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catch
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{
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parentNode.RemoveChild(node);
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}
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}
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#endregion
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#region 过滤属性
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for (int currentAttributeIndex = 0; currentAttributeIndex < node.Attributes.Count; currentAttributeIndex++)
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{
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HtmlAttribute attribute = node.Attributes[currentAttributeIndex];
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string name = attribute.Name, _value = attribute.Value;
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var attr = tag.AllowedAttribute(name);
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#region 如果是白名单之外的属性移除掉
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if (attr == null)
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{
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node.Attributes.Remove(name);
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currentAttributeIndex--;
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continue;
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}
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#endregion
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#region 元素内嵌样式
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if ("style".Equals(name, StringComparison.OrdinalIgnoreCase))
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{
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try
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{
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attribute.Value = CssFilter.Filters(_value,true);
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}
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catch
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{
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node.Attributes.Remove(name);
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currentAttributeIndex--;
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}
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continue;
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}
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#endregion
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///如果未能通过验证，将执行指定的操作
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if (!FilterPolicy.ValidateAttribute(attr,_value))
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{
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switch (attr.OnInvalid)
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{
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case PolicyHtmlAttributeOnInvalid.RemoveTag:
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//删除当前的元素并退出函数
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parentNode.RemoveChild(node);
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return;
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case PolicyHtmlAttributeOnInvalid.FilterTag:
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///删除当前节点，但保留其有效的子节点
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PromoteChildren(node);
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return;
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default:
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//删除当前的属性，指针往回调
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node.Attributes.Remove(attr.Name);
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currentAttributeIndex--;
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break;
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}
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}
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}
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#endregion
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///过滤当前元素的子节点
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FiltersTags(node.ChildNodes);
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}
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void FilterAction(HtmlNode node)
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{
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FiltersTags(node.ChildNodes);
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}
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/// <summary>
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/// 删除所有的属性和子元素，但保留文本和备注节点
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/// </summary>
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/// <param name="node"></param>
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void TruncateAction(HtmlNode node)
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{
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HtmlAttributeCollection attrs = node.Attributes;
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while (attrs.Count > 0)
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{
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node.Attributes.Remove(attrs[0].Name);
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}
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HtmlNodeCollection nodes = node.ChildNodes;
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int position = 0;
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while (nodes.Count > position)
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{
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HtmlNode nodeToRemove = nodes[position];
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var type = nodeToRemove.NodeType;
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if (type == HtmlNodeType.Text || type == HtmlNodeType.Comment) { position++; continue; }
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node.RemoveChild(nodeToRemove);
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}
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}
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/// <summary>
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/// 去除无效的XML字符
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/// </summary>
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/// <param name="in_Renamed"></param>
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/// <returns></returns>
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string StripNonValidXMLCharacters(string in_Renamed)
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{
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StringBuilder out_Renamed = new StringBuilder();
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char current;
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if (in_Renamed == null || ("".Equals(in_Renamed)))
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return "";
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for (int i = 0; i < in_Renamed.Length; i++)
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{
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current = in_Renamed[i];
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if ((current == 0x9) || (current == 0xA) || (current == 0xD) || ((current >= 0x20) && (current <= 0xD7FF)) || ((current >= 0xE000) && (current <= 0xFFFD)))
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out_Renamed.Append(current);
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}
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return out_Renamed.ToString();
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}
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/// <summary>
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/// 将指定节点从父节点中移除，但其子节点保留
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/// </summary>
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/// <param name="node"></param>
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void PromoteChildren(HtmlNode node)
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{
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///过滤子节点
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FiltersTags(node.ChildNodes);
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HtmlNodeCollection nodeList = node.ChildNodes;
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HtmlNode parent = node.ParentNode;
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///将它的所有子节点往上移到父节点的前面
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while (nodeList.Count > 0)
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{
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HtmlNode removeNode = node.RemoveChild(nodeList[0]);
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parent.InsertBefore(removeNode, node);
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}
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//然后将节点删除
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parent.RemoveChild(node);
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}
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#endregion
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}
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}
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