Uri.EscapeDataStringにRFC3986の動作をさせることができなかったので、私は独自のRFC3986準拠のエスケープメソッドを作成しました。Uri.EscapeDataStringを利用してから、エスケープをRFC3986準拠に「アップグレード」します。
/// <summary>
/// The set of characters that are unreserved in RFC 2396 but are NOT unreserved in RFC 3986.
/// </summary>
private static readonly string[] UriRfc3986CharsToEscape = new[] { "!", "*", "'", "(", ")" };
/// <summary>
/// Escapes a string according to the URI data string rules given in RFC 3986.
/// </summary>
/// <param name="value">The value to escape.</param>
/// <returns>The escaped value.</returns>
/// <remarks>
/// The <see cref="Uri.EscapeDataString"/> method is <i>supposed</i> to take on
/// RFC 3986 behavior if certain elements are present in a .config file. Even if this
/// actually worked (which in my experiments it <i>doesn't</i>), we can't rely on every
/// host actually having this configuration element present.
/// </remarks>
internal static string EscapeUriDataStringRfc3986(string value) {
// Start with RFC 2396 escaping by calling the .NET method to do the work.
// This MAY sometimes exhibit RFC 3986 behavior (according to the documentation).
// If it does, the escaping we do that follows it will be a no-op since the
// characters we search for to replace can't possibly exist in the string.
StringBuilder escaped = new StringBuilder(Uri.EscapeDataString(value));
// Upgrade the escaping to RFC 3986, if necessary.
for (int i = 0; i < UriRfc3986CharsToEscape.Length; i++) {
escaped.Replace(UriRfc3986CharsToEscape[i], Uri.HexEscape(UriRfc3986CharsToEscape[i][0]));
}
// Return the fully-RFC3986-escaped string.
return escaped.ToString();
}