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WebUtilityWrapper.cs
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WebUtilityWrapper.cs
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using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Net;
namespace MyNamespace
{
public static class WebUtilityWrapper
{
private static readonly char[] _htmlEntityEndingChars = new char[] { ';', '&' };
/// <summary>
/// A wrapper over Html Encode to help encode into valid HTML Entity Names (if present). It uses the same
/// dataset used by the framework to do HtmlDecode so that decoding works fine.
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
public static string HtmlEncode(string value)
{
// Calling the framework's HtmlEncode which takes care of encoding 5 hardcoded characters (<, >, ", \, &)
// and converts High ASCII (160 to 255) to their unicode representation (i.e   etc)
string response = WebUtility.HtmlEncode(value);
// First, we take care of all unicode characters that have corresponding html entity names and haven't
// been touched by the framework. We use the same lookup table that the framework leverages for Html.Decode
// so that decoding works for all. Examples: Greek letters (Δ or Δ)
string output = "";
foreach (var ch in response)
{
string entity = HtmlEntities.Lookup(ch);
output += string.IsNullOrEmpty(entity) ? ch + "" : $"&{entity};";
}
// For high ASCII characters (from 160 - 255), the framework's HtmlEncode method converts
// them into   and so on. So in these step we parse these, check the lookup table for corresponding
// HTML entity names and then, replace them if present.
// For more: http://referencesource.microsoft.com/#System/net/System/Net/WebUtility.cs,117
// Example ¢ is converted to ¢ by the framework, we must convert it into ¢ instead.
StringWriter writer = new StringWriter(CultureInfo.InvariantCulture);
HtmlEncode(output, writer);
return writer.ToString();
}
/// <summary>
/// This private method takes care of converting all high ASCII characters (160 - 255) into their
/// HTML entity names (if present).
/// </summary>
/// <param name="value"></param>
/// <param name="output"></param>
private static void HtmlEncode(string value, TextWriter output)
{
if (value == null)
{
return;
}
if (output == null)
{
throw new ArgumentNullException("output");
}
int l = value.Length;
for (int i = 0; i < l; i++)
{
char ch = value[i];
if (ch == '&')
{
// We found a '&'. Now look for the next ';' or '&'. The idea is that
// if we find another '&' before finding a ';', then this is not an entity,
// and the next '&' might start a real entity (VSWhidbey 275184)
int index = value.IndexOfAny(_htmlEntityEndingChars, i + 1);
if (index > 0 && value[index] == ';')
{
string entity = value.Substring(i + 1, index - i - 1);
if (entity.Length > 1 && entity[0] == '#')
{
// The # syntax can be in decimal or hex, e.g.
// å --> decimal
// å --> same char in hex
// See http://www.w3.org/TR/REC-html40/charset.html#entities
bool parsedSuccessfully;
uint parsedValue;
if (entity[1] == 'x' || entity[1] == 'X')
{
parsedSuccessfully = UInt32.TryParse(entity.Substring(2), NumberStyles.AllowHexSpecifier, NumberFormatInfo.InvariantInfo, out parsedValue);
}
else
{
parsedSuccessfully = UInt32.TryParse(entity.Substring(1), NumberStyles.Integer, NumberFormatInfo.InvariantInfo, out parsedValue);
}
if (parsedSuccessfully)
{
var entityName = HtmlEntities.Lookup((char)parsedValue);
if (string.IsNullOrEmpty(entityName))
output.Write((char)parsedValue);
else
output.Write($"&{entityName};");
i = index; // already looked at everything until semicolon
continue;
}
}
}
}
output.Write(ch);
}
}
#region HtmlEntities nested class
// Helper class for lookup of HTML encoding entities. This class has been referenced
// from: http://referencesource.microsoft.com/#System/net/System/Net/WebUtility.cs,792
// and up-to date as on 01/05/2017 (1st May '17)
private static class HtmlEntities
{
// The list is from http://www.w3.org/TR/REC-html40/sgml/entities.html, except for ', which
// is defined in http://www.w3.org/TR/2008/REC-xml-20081126/#sec-predefined-ent.
private static String[] _entitiesList = new String[] {
"\x0022-quot",
"\x0026-amp",
"\x0027-apos",
"\x003c-lt",
"\x003e-gt",
"\x00a0-nbsp",
"\x00a1-iexcl",
"\x00a2-cent",
"\x00a3-pound",
"\x00a4-curren",
"\x00a5-yen",
"\x00a6-brvbar",
"\x00a7-sect",
"\x00a8-uml",
"\x00a9-copy",
"\x00aa-ordf",
"\x00ab-laquo",
"\x00ac-not",
"\x00ad-shy",
"\x00ae-reg",
"\x00af-macr",
"\x00b0-deg",
"\x00b1-plusmn",
"\x00b2-sup2",
"\x00b3-sup3",
"\x00b4-acute",
"\x00b5-micro",
"\x00b6-para",
"\x00b7-middot",
"\x00b8-cedil",
"\x00b9-sup1",
"\x00ba-ordm",
"\x00bb-raquo",
"\x00bc-frac14",
"\x00bd-frac12",
"\x00be-frac34",
"\x00bf-iquest",
"\x00c0-Agrave",
"\x00c1-Aacute",
"\x00c2-Acirc",
"\x00c3-Atilde",
"\x00c4-Auml",
"\x00c5-Aring",
"\x00c6-AElig",
"\x00c7-Ccedil",
"\x00c8-Egrave",
"\x00c9-Eacute",
"\x00ca-Ecirc",
"\x00cb-Euml",
"\x00cc-Igrave",
"\x00cd-Iacute",
"\x00ce-Icirc",
"\x00cf-Iuml",
"\x00d0-ETH",
"\x00d1-Ntilde",
"\x00d2-Ograve",
"\x00d3-Oacute",
"\x00d4-Ocirc",
"\x00d5-Otilde",
"\x00d6-Ouml",
"\x00d7-times",
"\x00d8-Oslash",
"\x00d9-Ugrave",
"\x00da-Uacute",
"\x00db-Ucirc",
"\x00dc-Uuml",
"\x00dd-Yacute",
"\x00de-THORN",
"\x00df-szlig",
"\x00e0-agrave",
"\x00e1-aacute",
"\x00e2-acirc",
"\x00e3-atilde",
"\x00e4-auml",
"\x00e5-aring",
"\x00e6-aelig",
"\x00e7-ccedil",
"\x00e8-egrave",
"\x00e9-eacute",
"\x00ea-ecirc",
"\x00eb-euml",
"\x00ec-igrave",
"\x00ed-iacute",
"\x00ee-icirc",
"\x00ef-iuml",
"\x00f0-eth",
"\x00f1-ntilde",
"\x00f2-ograve",
"\x00f3-oacute",
"\x00f4-ocirc",
"\x00f5-otilde",
"\x00f6-ouml",
"\x00f7-divide",
"\x00f8-oslash",
"\x00f9-ugrave",
"\x00fa-uacute",
"\x00fb-ucirc",
"\x00fc-uuml",
"\x00fd-yacute",
"\x00fe-thorn",
"\x00ff-yuml",
"\x0152-OElig",
"\x0153-oelig",
"\x0160-Scaron",
"\x0161-scaron",
"\x0178-Yuml",
"\x0192-fnof",
"\x02c6-circ",
"\x02dc-tilde",
"\x0391-Alpha",
"\x0392-Beta",
"\x0393-Gamma",
"\x0394-Delta",
"\x0395-Epsilon",
"\x0396-Zeta",
"\x0397-Eta",
"\x0398-Theta",
"\x0399-Iota",
"\x039a-Kappa",
"\x039b-Lambda",
"\x039c-Mu",
"\x039d-Nu",
"\x039e-Xi",
"\x039f-Omicron",
"\x03a0-Pi",
"\x03a1-Rho",
"\x03a3-Sigma",
"\x03a4-Tau",
"\x03a5-Upsilon",
"\x03a6-Phi",
"\x03a7-Chi",
"\x03a8-Psi",
"\x03a9-Omega",
"\x03b1-alpha",
"\x03b2-beta",
"\x03b3-gamma",
"\x03b4-delta",
"\x03b5-epsilon",
"\x03b6-zeta",
"\x03b7-eta",
"\x03b8-theta",
"\x03b9-iota",
"\x03ba-kappa",
"\x03bb-lambda",
"\x03bc-mu",
"\x03bd-nu",
"\x03be-xi",
"\x03bf-omicron",
"\x03c0-pi",
"\x03c1-rho",
"\x03c2-sigmaf",
"\x03c3-sigma",
"\x03c4-tau",
"\x03c5-upsilon",
"\x03c6-phi",
"\x03c7-chi",
"\x03c8-psi",
"\x03c9-omega",
"\x03d1-thetasym",
"\x03d2-upsih",
"\x03d6-piv",
"\x2002-ensp",
"\x2003-emsp",
"\x2009-thinsp",
"\x200c-zwnj",
"\x200d-zwj",
"\x200e-lrm",
"\x200f-rlm",
"\x2013-ndash",
"\x2014-mdash",
"\x2018-lsquo",
"\x2019-rsquo",
"\x201a-sbquo",
"\x201c-ldquo",
"\x201d-rdquo",
"\x201e-bdquo",
"\x2020-dagger",
"\x2021-Dagger",
"\x2022-bull",
"\x2026-hellip",
"\x2030-permil",
"\x2032-prime",
"\x2033-Prime",
"\x2039-lsaquo",
"\x203a-rsaquo",
"\x203e-oline",
"\x2044-frasl",
"\x20ac-euro",
"\x2111-image",
"\x2118-weierp",
"\x211c-real",
"\x2122-trade",
"\x2135-alefsym",
"\x2190-larr",
"\x2191-uarr",
"\x2192-rarr",
"\x2193-darr",
"\x2194-harr",
"\x21b5-crarr",
"\x21d0-lArr",
"\x21d1-uArr",
"\x21d2-rArr",
"\x21d3-dArr",
"\x21d4-hArr",
"\x2200-forall",
"\x2202-part",
"\x2203-exist",
"\x2205-empty",
"\x2207-nabla",
"\x2208-isin",
"\x2209-notin",
"\x220b-ni",
"\x220f-prod",
"\x2211-sum",
"\x2212-minus",
"\x2217-lowast",
"\x221a-radic",
"\x221d-prop",
"\x221e-infin",
"\x2220-ang",
"\x2227-and",
"\x2228-or",
"\x2229-cap",
"\x222a-cup",
"\x222b-int",
"\x2234-there4",
"\x223c-sim",
"\x2245-cong",
"\x2248-asymp",
"\x2260-ne",
"\x2261-equiv",
"\x2264-le",
"\x2265-ge",
"\x2282-sub",
"\x2283-sup",
"\x2284-nsub",
"\x2286-sube",
"\x2287-supe",
"\x2295-oplus",
"\x2297-otimes",
"\x22a5-perp",
"\x22c5-sdot",
"\x2308-lceil",
"\x2309-rceil",
"\x230a-lfloor",
"\x230b-rfloor",
"\x2329-lang",
"\x232a-rang",
"\x25ca-loz",
"\x2660-spades",
"\x2663-clubs",
"\x2665-hearts",
"\x2666-diams",
};
private static Dictionary<char, string> _lookupTable = GenerateLookupTable();
private static Dictionary<char, string> GenerateLookupTable()
{
// e[0] is unicode char, e[1] is '-', e[2+] is entity string
Dictionary<char, string> lookupTable = new Dictionary<char, string>();
foreach (string e in _entitiesList)
{
lookupTable.Add(e[0], e.Substring(2));
}
return lookupTable;
}
public static string Lookup(char theChar)
{
if (theChar == ';' || theChar == '&' || theChar == '#')
return null;
string entity;
_lookupTable.TryGetValue(theChar, out entity);
return entity;
}
}
#endregion
}
}