判斷網頁編碼的五種解法（這些都不是最完美的，那個研究中...）

(1)原始方案
System.Text.Encoding.Default
採用當前的默認編碼，可以解決大部分問題，但是很多跟情況下同樣會出錯。

(2)HTTPWebrequest 的CharacterSet（MSND上給的方案，本來應該的做法）
該屬性可以返回該網站編碼，但是總爲空。

(3)老外的解決之道
Sven Groot
I came across a very silly (and annoying) bug in the HttpWebResponse.CharacterSet property. Let's see if you can spot it (code extracted with reflector):

public string get_CharacterSet() { this.CheckDisposed(); string text1 = this.m_HttpResponseHeaders.ContentType; if ((this.m_CharacterSet == null) && !ValidationHelper.IsBlankString(text1)) { this.m_CharacterSet = string.Empty; string text2 = text1.ToLower(CultureInfo.InvariantCulture); if (text2.Trim().StartsWith("text/")) { this.m_CharacterSet = "ISO-8859-1"; } int num1 = text2.IndexOf(";"); if (num1 > 0) { while ((num1 = text2.IndexOf("charset", num1)) >= 0) { num1 += 7; if ((text2[num1 - 8] == ';') || (text2[num1 - 8] == ' ')) { while ((num1 < text2.Length) && (text2[num1] == ' ')) { num1++; } if ((num1 < (text2.Length - 1)) && (text2[num1] == '=')) { num1++; int num2 = text2.IndexOf(';', num1); if (num2 > num1) { this.m_CharacterSet = text1.Substring(num1, num2).Trim(); break; } this.m_CharacterSet = text1.Substring(num1).Trim(); break; } } } } } return this.m_CharacterSet; }

 

(4)另一種方法（先獲取內容，再根據內容來判）

static string GetHtml(string url, Encoding encoding) { byte[] buf = new WebClient().DownloadData(url); if (encoding != null) return encoding.GetString(buf); string html = Encoding.UTF8.GetString(buf); encoding = GetEncoding(html); if (encoding == null || encoding == Encoding.UTF8) return html; return encoding.GetString(buf); }

(5)結合3/4的辦法（當然去看HttpWebResponse函數的源代碼了）
//得到CharacterSet

private string getEncoding (HttpWebResponse httpResp) { string contentType = httpResp.ContentType ; int i = contentType.IndexOf("charset="); if (i>=0) { i += 8; int j = contentType.IndexOf(';', i); if (j>=i) { return contentType.Substring(i,j-i).Trim(); } return contentType.Substring(i); } return string.Empty;}