对编码内容多次UrlDecode

public static string UrlDecode(string encodedValue) ???????{ ???????????if (encodedValue == null) ???????????????return null; ????????????return UrlDecodeInternal(encodedValue, Encoding.UTF8); ???????}

private static string UrlDecodeInternal(string value, Encoding encoding) ???????{ ???????????if (value == null) ???????????{ ???????????????return null; ???????????} ????????????int count = value.Length; ???????????UrlDecoder helper = new UrlDecoder(count, encoding); ????????????// go through the string‘s chars collapsing %XX and ???????????// appending each char as char, with exception of %XX constructs ???????????// that are appended as bytes ????????????for (int pos = 0; pos < count; pos++) ???????????{ ???????????????char ch = value[pos]; ????????????????if (ch == ‘+‘) ???????????????{ ???????????????????ch = ‘ ‘; ???????????????} ???????????????else if (ch == ‘%‘ && pos < count - 2) ???????????????{ ???????????????????int h1 = HexToInt(value[pos + 1]); ???????????????????int h2 = HexToInt(value[pos + 2]); ????????????????????if (h1 >= 0 && h2 >= 0) ???????????????????{ ????// valid 2 hex chars ???????????????????????byte b = (byte)((h1 << 4) | h2); ???????????????????????pos += 2; ????????????????????????// don‘t add as char ???????????????????????helper.AddByte(b); ???????????????????????continue; ???????????????????} ???????????????} ????????????????if ((ch & 0xFF80) == 0) ???????????????????helper.AddByte((byte)ch); // 7 bit have to go as bytes because of Unicode ???????????????else ???????????????????helper.AddChar(ch); ???????????} ????????????return helper.GetString(); ???????}

 internal void AddChar(char ch) ???????????{ ???????????????if (_numBytes > 0) ???????????????????FlushBytes(); ????????????????_charBuffer[_numChars++] = ch; ???????????}

 ?internal void AddByte(byte b) ???????????{ ???????????????if (_byteBuffer == null) ???????????????????_byteBuffer = new byte[_bufferSize]; ????????????????_byteBuffer[_numBytes++] = b; ???????????}

 internal String GetString() ???????????{ ???????????????if (_numBytes > 0) ???????????????????FlushBytes(); ????????????????if (_numChars > 0) ???????????????????return new String(_charBuffer, 0, _numChars); ???????????????else ???????????????????return String.Empty; ???????????}

 ???????// Creates a new string from the characters in a subarray. ?The new string will ???????// be created from the characters in value between startIndex and ???????// startIndex + length - 1. ???????// ???????[System.Security.SecuritySafeCritical] ?// auto-generated ???????[ResourceExposure(ResourceScope.None)] ???????[MethodImplAttribute(MethodImplOptions.InternalCall)] ???????public extern String(char [] value, int startIndex, int length);