C # turns HTML into plain text

////// converts HTML to plain text.///Class htmltotext{//static data tables protected static Dictionary
 
  _tags; protected static HashSet
  
   _ignoretags;    Instance variables protected Textbuilder _text;    protected string _html;     protected int _pos; Static constructor (one time only) static Htmltotext () {_tags = new Dictionary
   
    
(); _tags.        ADD ("Address", "\ n"); _tags.        ADD ("blockquote", "\ n"); _tags.        Add ("div", "\ n"); _tags.        ADD ("DL", "\ n"); _tags.        ADD ("fieldset", "\ n"); _tags.        ADD ("form", "\ n"); _tags.        ADD ("H1", "\ n"); _tags.        ADD ("/h1", "\ n"); _tags.        ADD ("H2", "\ n"); _tags.        ADD ("/h2", "\ n"); _tags.        ADD ("H3", "\ n"); _tags.        ADD ("/h3", "\ n"); _tags.        ADD ("H4", "\ n"); _tags.        ADD ("/h4", "\ n"); _tags.        Add ("h5", "\ n"); _tags.        ADD ("/h5", "\ n"); _tags.        Add ("h6", "\ n"); _tags.        ADD ("/h6", "\ n"); _tags.        ADD ("P", "\ n"); _tags.        ADD ("/P", "\ n"); _tags.        ADD ("table", "\ n"); _tags.        ADD ("/table", "\ n"); _tags.        ADD ("ul", "\ n"); _tags.        ADD ("/ul", "\ n"); _tags.        ADD ("ol", "\ n"); _tags.        ADD ("/ol", "\ n"); _tags.        ADD ("/li", "\ n"); _tags.        ADD ("br", "\ n"); _tags.        ADD ("/td", "\ T"); _tags.        ADD ("/tr", "\ n"); _tags.         ADD ("/pre", "\ n"); _ignoretags = NEW HashSet 
    
     ();        _ignoretags.add ("script");        _ignoretags.add ("NoScript");        _ignoretags.add ("style");    _ignoretags.add ("Object"); }     ///
     // Converts the given HTML to plain text and returns the result. /// ///
     HTML to be converted///
     
      
       resulting plain text
      
     public string Convert (string html) {//Initialize state variables _text = new Textbuilder ();        _html = html;         _pos = 0; Process input while (! Endoftext) {if (Peek () = = < ') {//HTML tag bool Selfclosi                Ng                 string tag = Parsetag (out selfclosing); Handle Special Tag Cases if (tag = = "Body") {//Discard content befor E                    _text.                Clear ();  } else if (tag = = "/body") {//Discard content after                    _pos = _html.                Length;                    } else if (tag = = "Pre") {//Enter preformatted mode _text.                    Preformatted = true;                Eatwhitespacetonextline ();                    } else if (tag = = "/pre") {//Exit preformatted mode _text.                preformatted = false;                } string value; if (_tags. TryGetValue (tag, out value)) _text.                 Write (value);            if (_ignoretags.contains (tag)) eatinnercontent (tag);                } else if (Char.iswhitespace (Peek ())) {//whitespace (treat all as space) _text. Write (_text. Preformatted?                Peek (): ");            Moveahead (); } else {//other text _text.                Write (Peek ());        Moveahead ();    }}//Return result return Httputility.htmldecode (_text.    ToString ()); }//Eats All characters that is part of the current tag//and returns information about that tag protected St        Ring Parsetag (out bool selfclosing) {string tag = String.Empty;         Selfclosing = false;             if (Peek () = = ' < ') {moveahead ();            Parse tag name Eatwhitespace ();            int start = _pos;            if (Peek () = = '/') moveahead (); while (! Endoftext &&!             Char.iswhitespace (Peek ()) && peek ()! = '/' && peek ()! = ' > ') moveahead (); Tag = _html. Substring (Start, _pos-start).             ToLower (); Parse Rest of Tag while (! Endoftext && peek ()! = ' > ') {if (Peek () = = ' "' | |                Peek () = = ' \ ') eatquotedvalue ();           else {         if (Peek () = = '/') selfclosing = true;                Moveahead ();        }} moveahead ();    } return tag; }//consumes inner content from the current tag protected void eatinnercontent (String tag) {string Endt         AG = "/" + tag; while (! Endoftext) {if (Peek () = = < ') {//consume a tag bool self                Closing;                if (Parsetag (out selfclosing) = = Endtag) return; Use recursion to consume nested tags if (!selfclosing &&!tag.            StartsWith ("/")) eatinnercontent (tag);        } else Moveahead ();        }}//Returns True if the current position are at the end of//the string protected bool Endoftext { get {return (_pos >= _html. Length);   }}//Safely returns the character at the current position protected char Peek () {return (_pos < _html. Length)?    _html[_pos]: (char) 0; }//Safely advances to current position to the next character protected void Moveahead () {_pos = MATH.M In (_pos + 1, _html.    Length);    }//Moves the current position to the next Non-whitespace//character.    protected void Eatwhitespace () {while (Char.iswhitespace (Peek ())) Moveahead ();    }//Moves the current position to the next Non-whitespace//character or the start of the next line, whichever            Comes first protected void Eatwhitespacetonextline () {while (Char.iswhitespace (Peek ())) {            char C = Peek ();            Moveahead ();        if (c = = ' \ n ') break; }}//Moves the current position past a quoted value protected void Eatquotedvalue () {char c = Peek (        ); if (c = = ' "' | |  c = = ' \ ') {//Opening quote moveahead ();          Find end of value int start = _pos; _pos = _html.            IndexOfAny (new char[] {c, ' \ R ', ' \ n '}, _pos); if (_pos < 0) _pos = _html.            Length;    else Moveahead ();  Closing Quote}}///
     // A StringBuilder class that helps eliminate excess whitespace. /// Protected class Textbuilder {private StringBuilder _text;        Private StringBuilder _currline;        private int _emptylines;         private bool _preformatted;            Construction public Textbuilder () {_text = new StringBuilder ();            _currline = new StringBuilder ();            _emptylines = 0;        _preformatted = false; }         ///
     /// Normally, extra whitespace characters is discarded. They is passed//through unchanged. /// public bool Preformatted {get {return _preformatted; } set {if (value) {//Clear line buffer if Changi ng to//preformatted mode if (_currline.length > 0) Flush                    Currline ();                _emptylines = 0;            } _preformatted = value; }        }         ///
     ///Clears all current text. /// public void Clear () {_text.            Length = 0;            _currline.length = 0;        _emptylines = 0; }         ///
     // writes the given string to the output buffer. /// ///
     public void Write (string s) {foreach (char C-in s) write (c); }         ///
     /// writes the given character to the output buffer. /// ///
     Character to write        public void Write (char c) {if (_preformatted) {//write preformatted Character _text.            Append (c); } else {if (c = = ' \ r ') {//Ignore carriage return                S. We ' ll process//' \ n ' If it comes next} else if (c = = ' \ n ')                {//Flush current line flushcurrline ();                    } else if (Char.iswhitespace (c)) {//Write single space character                    int len = _currline.length; if (len = = 0 | |!                Char.iswhitespace (_currline[len-1]) _currline.append ("); } else {//ADD character to _currline.ap                Pend (c); }            }        }         //Appends the current line to output buffer protected void Flushcurrline () {//Get current line String line = _currline.tostring ().             Trim (); Determine if line contains non-space characters string tmp = line.            Replace ("", String.Empty); if (TMP.                Length = = 0) {//an empty line _emptylines++; if (_emptylines < 2 && _text. Length > 0) _text.            Appendline (line);                } else {//A non-empty line _emptylines = 0; _text.            Appendline (line);        }//Reset current line _currline.length = 0;  }         ///
     //Returns The current output as a string. /// public override string ToString () {if (_currline.length > 0) flushcurrline (); Return _text.        ToString (); }    }}
    
   
  
 

