CODEWITHSUNDEEP
c#htmlunicodewebclientsystem.net
IIRawCodeII
IIRawCodeII

Reputation: 395

Kanji characters from WebClient html different from actual Kanji in website

So, I'm trying to get a portion of text from a website called Kanji-A-Day.com, but I have a problem.

You see, I'm trying to get the daily kanji from the website, and I was able to narrow the HTML down to what I want, but it seems the characters are different..?

What it looks like

What it should look like

What's even more strange is that I produced the results for the second image by copying and pasting directly from the site, so it's not a font problem.

Here's the code I use for getting the character:

public void UpdateDailyKanji() // Called at the initialization of a new main form
{
    string kanji;
    using (WebClient client = new WebClient()) // Grab the string 
        kanji = client.DownloadString("http://www.kanji-a-day.com/level4/index.php"); 
    // Trim the HTML to just the Kanji
    kanji = kanji.Remove(0, kanji.IndexOf(@"<div class=""glyph"">") + 19);
    kanji = kanji.Remove(kanji.IndexOf("</div>")-2);
    kanji = kanji.Trim();
    Text_DailyKanji.Text = kanji; // Set the Kanji
}

Does anyone know what's going on here? I'm guessing it's some Unicode thing but I don't know much about it.

Thanks in advance.

Upvotes: 2

Views: 579

Answers (1)

Jimi
Jimi

Reputation: 32278

The page you're trying to download as a string is encoded using charset=EUC-JP, also known as Japanese (EUC) (CodePage 51932). This is clearly set in the page headers.

Why is the string returned by WebClient.DownloadString encoded using the wrong encoder?

The MSDN Docs state this:

This method retrieves the specified resource. After it downloads the resource, the method uses the encoding specified in the Encoding property to convert the resource to a String.

Thus, you have to know beforehand what encoding will be used and specify it, setting the WebClient.Encoding property.

To verify this, check the .NET Reference Source for the WebClient.DownloadString method:

try {
    WebRequest request;
    byte [] data = DownloadDataInternal(address, out request);
    string stringData = GetStringUsingEncoding(request, data);
    if(Logging.On)Logging.Exit(Logging.Web, this, "DownloadString", stringData);
    return stringData;
    } finally {
        CompleteWebClientState();
    }

The encoding is set using the Request settings, not the Response ones.
The result is, the downloaded string is encoded using the default CodePage.

What you can do now is:

  • Download the page twice, the first time to check whether the WebClient encoding and the Html page encoding don't match.
  • Re-encode the string with the correct encoding, set in the underlying WebResponse.
  • Don't use WebClient, use HttpClient or WebRequest directly. Or, if you like this tool, create a custom WebClient class to handle the WebRequest/WebResponse in a more direct way.

This is a method to perform the re-encoding task:
The string returned by WebClient is converted to a Byte Array and passed to a MemoryStream, then re-encoded using a StreamReader with the Encoding retrieved from the Content-Type: charset Response Header.

EDIT:
Now using Reflection to get the page Encoding from the underlying HttpWebResponse. This should avoid errors in parsing the original CharacterSet as defined by the remote response.

using System.IO;
using System.Net;
using System.Reflection;
using System.Text;

public string WebClient_DownLoadString(Uri uri)
{
    using (var client = new WebClient())
    {
        // If Windows 7 - Windows Server 2008 R2
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

        client.CachePolicy = new System.Net.Cache.RequestCachePolicy(System.Net.Cache.RequestCacheLevel.BypassCache);
        client.Headers.Add(HttpRequestHeader.Accept, "ext/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
        client.Headers.Add(HttpRequestHeader.AcceptLanguage, "en-US,en;q=0.8");
        client.Headers.Add(HttpRequestHeader.KeepAlive, "keep-alive");

        string result = client.DownloadString(uri);

        var flags = BindingFlags.Instance | BindingFlags.NonPublic;
        using (var response = (HttpWebResponse)client.GetType().GetField("m_WebResponse", flags).GetValue(client))
        {
            var pageEncoding = Encoding.GetEncoding(wc_response.CharacterSet);
            byte[] bytes = client.Encoding.GetBytes(result);
            using (var ms = new MemoryStream(bytes, 0, bytes.Length))
            using (var reader = new StreamReader(ms, pageEncoding))
            {
                ms.Position = 0;
                return reader.ReadToEnd();
            };
        };
    }
}

Now your code should get the Japanese characters in their correct form.

Uri uri = new Uri("http://www.kanji-a-day.com/level4/index.php", UriKind.Absolute);
string kanji = WebClient_DownLoadString(uri);

kanji = kanji.Remove(0, kanji.IndexOf("<div class=\"glyph\">") + 19);
kanji = kanji.Remove(kanji.IndexOf("</div>")-2);
kanji = kanji.Trim();

Text_DailyKanji.Text = kanji;

Upvotes: 2

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