static void Main(string[] args){
  string Nd = UnicodeExpansion(System.Globalization.UnicodeCategory.DecimalDigitNumber);
  Console.WriteLine(Nd);
  Console.ReadLine();
}

/// <summary>
/// Expands a Unicode character set into an ECMAScript compatible character
/// range string.
/// </summary>
/// <param name="category">
/// The Unicode character category to expand.
/// </param>
/// <returns>
/// A <see cref="System.String" /> that can be used in an ECMAScript regular
/// expression.
/// </returns>
/// <remarks>
/// <para>
/// ECMAScript (JavaScript) does not inherently understand Unicode in regular
/// expressions, which results in incorrect validation when using character
/// classes (\w, \s, \d, etc.).
/// </para>
/// <para>
/// This method expands a <see cref="System.Globalization.UnicodeCategory" />
/// into a string that can be used in an ECMAScript regular expression.  For
/// example, the category <see cref="System.Globalization.UnicodeCategory.LetterNumber" />
/// expands to <c>\u2160-\u2183\u3007\u3021-\u3029\u3038-\u303a</c>.
/// </para>
/// </remarks>
public static string UnicodeExpansion(System.Globalization.UnicodeCategory category){
  // The fully expanded block of characters
  string expansion = "";
  // Low-end of the character block
  int blockLow = -1;
  // High-end of the character block
  int blockHigh = -1;
  // Marks whether the current block has been written
  bool blockWritten = false;

  for(int charVal = 0; charVal <= Char.MaxValue; charVal++){
    // Get the category of the current character
    System.Globalization.UnicodeCategory charCat = Char.GetUnicodeCategory(Convert.ToChar(charVal));

    // We haven't written anything this loop; used to ensure
    // all blocks get written at the end.
    blockWritten = false;

    // Ignore characters that don't match the category.
    if(charCat != category){
      continue;
    }

    if(blockLow == -1){
      // Handle the very first block
      blockLow = charVal;
      blockHigh = charVal;
    }
    else if(
      // charVal skipped some characters OR
      blockHigh + 1 != charVal ||
      // We're at the end of the set of characters
      blockHigh + 1 > Char.MaxValue
      ){

      // Write the block to the expansion string
      if(blockLow == blockHigh){
        // This is a one-character block
        expansion += String.Format(@"\u{0:x4}", blockLow);
      }
      else{
        // This is a multi-char block
        expansion += String.Format(@"\u{0:x4}-\u{1:x4}", blockLow, blockHigh);
      }

      // Start a new block
      blockWritten = true;
      blockLow = charVal;
      blockHigh = charVal;
    }
    else{
      // We're still in the same block; increment the high end of the block.
      blockHigh = charVal;
    }
  }

  // If we didn't write the last block, write it now
  if(!blockWritten){
    if(blockLow == blockHigh){
      // This is a one-character block
      expansion += String.Format(@"\u{0:x4}", blockLow);
    }
    else{
      // This is a multi-char block
      expansion += String.Format(@"\u{0:x4}-\u{1:x4}", blockLow, blockHigh);
    }
    blockWritten = true;
  }

  return expansion;
}