Converting HTML entities to Unicode Characters in C#

Question

I found similar questions and answers for Python and Javascript, but not for C# or any other WinRT compatible language.

The reason I think I need it, is because I\'

Answer 1

Different coding/encoding of HTML entities and HTML numbers in Metro App and WP8 App.

With Windows Runtime Metro App

{
    string inStr = "ó";
    string auxStr = System.Net.WebUtility.HtmlEncode(inStr);
    // auxStr == ó
    string outStr = System.Net.WebUtility.HtmlDecode(auxStr);
    // outStr == ó
    string outStr2 = System.Net.WebUtility.HtmlDecode("ó");
    // outStr2 == ó
}

With Windows Phone 8.0

{
    string inStr = "ó";
    string auxStr = System.Net.WebUtility.HtmlEncode(inStr);
    // auxStr == ó
    string outStr = System.Net.WebUtility.HtmlDecode(auxStr);
    // outStr == ó
    string outStr2 = System.Net.WebUtility.HtmlDecode("ó");
    // outStr2 == ó
}

To solve this, in WP8, I have implemented the table in HTML ISO-8859-1 Reference before calling System.Net.WebUtility.HtmlDecode().

Answer 2

This worked for me, replaces both common and unicode entities.

private static readonly Regex HtmlEntityRegex = new Regex("&(#)?([a-zA-Z0-9]*);");

public static string HtmlDecode(this string html)
{
    if (html.IsNullOrEmpty()) return html;
    return HtmlEntityRegex.Replace(html, x => x.Groups[1].Value == "#"
        ? ((char)int.Parse(x.Groups[2].Value)).ToString()
        : HttpUtility.HtmlDecode(x.Groups[0].Value));
}

[Test]
[TestCase(null, null)]
[TestCase("", "")]
[TestCase("'fark'", "'fark'")]
[TestCase(""fark"", "\"fark\"")]
public void should_remove_html_entities(string html, string expected)
{
    html.HtmlDecode().ShouldEqual(expected);
}

Answer 3

This might be useful, replaces all (for as far as my requirements go) entities with their unicode equivalent.

    public string EntityToUnicode(string html) {
        var replacements = new Dictionary<string, string>();
        var regex = new Regex("(&[a-z]{2,5};)");
        foreach (Match match in regex.Matches(html)) {
            if (!replacements.ContainsKey(match.Value)) { 
                var unicode = HttpUtility.HtmlDecode(match.Value);
                if (unicode.Length == 1) {
                    replacements.Add(match.Value, string.Concat("&#", Convert.ToInt32(unicode[0]), ";"));
                }
            }
        }
        foreach (var replacement in replacements) {
            html = html.Replace(replacement.Key, replacement.Value);
        }
        return html;
    }

Answer 4

Improved Zumey method (I can`t comment there). Max char size is in the entity: &exclamation; (11). Upper case in the entities are also possible, ex. À (Source from wiki)

public string EntityToUnicode(string html) {
        var replacements = new Dictionary<string, string>();
        var regex = new Regex("(&[a-zA-Z]{2,11};)");
        foreach (Match match in regex.Matches(html)) {
            if (!replacements.ContainsKey(match.Value)) { 
                var unicode = HttpUtility.HtmlDecode(match.Value);
                if (unicode.Length == 1) {
                    replacements.Add(match.Value, string.Concat("&#", Convert.ToInt32(unicode[0]), ";"));
                }
            }
        }
        foreach (var replacement in replacements) {
            html = html.Replace(replacement.Key, replacement.Value);
        }
        return html;
    }

Answer 5

Use HttpUtility.HtmlDecode() .Read on msdn here

decodedString = HttpUtility.HtmlDecode(myEncodedString)

Answer 6

I recommend using System.Net.WebUtility.HtmlDecode and NOT HttpUtility.HtmlDecode.

This is due to the fact that the System.Web reference does not exist in Winforms/WPF/Console applications and you can get the exact same result using this class (which is already added as a reference in all those projects).

Usage:

string s =  System.Net.WebUtility.HtmlDecode("é"); // Returns é