public static char IntToHex(int n)
{ if (n <= 9){ return (char) (n + 0x30);} return (char) ((n - 10) + 0x61);
}

public static bool IsUrlSafeChar(char ch)
{ if ((((ch >= 'a') && (ch <= 'z')) || ((ch >= 'A') && (ch <= 'Z'))) || ((ch >= '0') && (ch <= '9'))){ return true;} switch (ch){ case '(': case ')': case '*': case '-': case '.': case '_': case '!': return true;} return false;
}

internal static string UrlEncodeSpaces(string str)
{ if ((str != null) && (str.IndexOf(' ') >= 0)){ str = str.Replace(" ", "%20");} return str;
}

public static unsafe void HtmlEncode(string value, TextWriter output)
{ if (value != null){ if (output == null){ throw new ArgumentNullException("output");} int num = IndexOfHtmlEncodingChars(value, 0); if (num == -1){ output.Write(value);} else { int num2 = value.Length - num; fixed (char* str = ((char*) value)){ char* chPtr = str; char* chPtr2 = chPtr; while (num-- > 0){ chPtr2++; output.Write(chPtr2[0]);} while (num2-- > 0){ chPtr2++; char ch = chPtr2[0]; if (ch <= '>'){ switch (ch){ case '&':{ output.Write("&amp;"); continue;} case '\'':{ output.Write("'"); continue;} case '"':{ output.Write("&quot;"); continue;} case '<':{ output.Write("&lt;"); continue;} case '>':{ output.Write("&gt;"); continue;}} output.Write(ch); continue;} if ((ch >= '\x00a0') && (ch < 'Ā')){ output.Write("&#"); output.Write(ch.ToString(NumberFormatInfo.InvariantInfo)); output.Write(';');} else { output.Write(ch);}}}}}
}

protected internal virtual byte[] UrlEncode(byte[] bytes, int offset, int count)
{ if (!ValidateUrlEncodingParameters(bytes, offset, count)){ return null;} int num = 0; int num2 = 0; for (int i = 0; i < count; i++){ char ch = (char) bytes[offset + i]; if (ch == ' '){ num++;} else if (!HttpEncoderUtility.IsUrlSafeChar(ch)){ num2++;}} if ((num == 0) && (num2 == 0)){ return bytes;} byte[] buffer = new byte[count + (num2 * 2)]; int num4 = 0; for (int j = 0; j < count; j++){ byte num6 = bytes[offset + j]; char ch2 = (char) num6; if (HttpEncoderUtility.IsUrlSafeChar(ch2)){ buffer[num4++] = num6;} else if (ch2 == ' '){ buffer[num4++] = 0x2b;} else { buffer[num4++] = 0x25; buffer[num4++] = (byte) HttpEncoderUtility.IntToHex((num6 >> 4) & 15); buffer[num4++] = (byte) HttpEncoderUtility.IntToHex(num6 & 15);}} return buffer;
}

protected internal virtual string UrlPathEncode(string value)
{ if (string.IsNullOrEmpty(value)){ return value;} int index = value.IndexOf('?'); if (index >= 0){ return (this.UrlPathEncode(value.Substring(0, index)) + value.Substring(index));} return HttpEncoderUtility.UrlEncodeSpaces(this.UrlEncodeNonAscii(value, Encoding.UTF8));
}

注意看这里。这就是差别。

int index = value.IndexOf('?');if (index >= 0){return (this.UrlPathEncode(value.Substring(0, index)) + value.Substring(index));}return HttpEncoderUtility.UrlEncodeSpaces(this.UrlEncodeNonAscii(value, Encoding.UTF8));

如果是path方法， 如果?号有任何值，则不再进行操作。直接传递。