I have page with this code is part of it:

<html dir="rtl">

<head>
<meta name="GENERATOR" content="Microsoft FrontPage 6.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
...

This page is served by IIS (on a winxp SP2 machine).
when i browse the page in IE ( on the same machine using http:// request)
the page is shown correctly.
But when i use this code to get the page the textboxHTMLSource shows
characters incorrectly (some garbage between some english text; the garbage
is actually some arabic, chinese ... text)

private void buttonGetUrl_Click(object sender, EventArgs e)
{
Uri url = new Uri(textBoxUrl.Text, UriKind.Absolute);
HttpWebRequest webrq =
(HttpWebRequest)HttpWebRequest.CreateDefault(url);
HttpWebResponse webresp = (HttpWebResponse)(webrq.GetResponse());
Stream resp = webresp.GetResponseStream();
byte[] data = new byte[webresp.ContentLength];
int len = resp.Read(data, 0, data.Length);
switch (webresp.ContentType)
{
case MediaTypeNames.Text.Html:
case MediaTypeNames.Text.Plain:
case MediaTypeNames.Text.RichText:
case MediaTypeNames.Text.Xml:
textBoxHTMLSource.Text =
Encoding.GetEncoding(webresp.CharacterSet).GetString(data, 0, len);
break;
default:
textBoxHTMLSource.Text = webresp.ContentType;
break;
}
}

I used the debugger to inspect some values in webresp object they are as
follows:

webresp.ContentType = "text/html"
webresp.ContentEncoding = ""
webresp.CharacterSet = "ISO-8859-1"
can any1 say why CharacterSet is ISO instead of utf-8?
how can i fix this?