using System;

using System.Text.RegularExpressions;

using System.Linq;

public static class Program

{

    public static void Main()

    {

        Console.WriteLine("helloWorld.presetAddress.streetName".ToPascalCase());

    }

      public static string ToPascalCase(this string original)

      {

          Regex invalidCharsRgx = new Regex("[^_a-zA-Z0-9]");

    Regex whiteSpace = new Regex(@"(?<=\s)");

    Regex startsWithLowerCaseChar = new Regex("^[a-z]");

    Regex firstCharFollowedByUpperCasesOnly = new Regex("(?<=[A-Z])[A-Z0-9]+$");

    Regex lowerCaseNextToNumber = new Regex("(?<=[0-9])[a-z]");

    Regex upperCaseInside = new Regex("(?<=[A-Z])[A-Z]+?((?=[A-Z][a-z])|(?=[0-9]))");

​

    // replace white spaces with undescore, then replace all invalid chars with empty string

    var pascalCase = invalidCharsRgx.Replace(whiteSpace.Replace(original, "_"), string.Empty)

        // split by underscores

        .Split(new char[] { '_' }, StringSplitOptions.RemoveEmptyEntries)

        // set first letter to uppercase

        .Select(w => startsWithLowerCaseChar.Replace(w, m => m.Value.ToUpper()))

        // replace second and all following upper case letters to lower if there is no next lower (ABC -> Abc)

        .Select(w => firstCharFollowedByUpperCasesOnly.Replace(w, m => m.Value.ToLower()))

        // set upper case the first lower case following a number (Ab9cd -> Ab9Cd)

        .Select(w => lowerCaseNextToNumber.Replace(w, m => m.Value.ToUpper()))

        // lower second and next upper case letters except the last if it follows by any lower (ABcDEf -> AbcDef)

        .Select(w => upperCaseInside.Replace(w, m => m.Value.ToLower()));

​

    return string.Concat(pascalCase);

      }

}