using System;

using System.Text;

// Marcos García Varela

public class Program

{

    public static void Main()

    {

        Console.WriteLine(new SentenceProcessor().InjectCapitals("Test string"));

    }

}

​

public class SentenceProcessor

{

    public string InjectCapitals(string input)

    {

        var stringBuilder = new StringBuilder();

        bool capitaliseNext = true;

        foreach (char character in input)

        {

            char characterToAppend = character;

            if (char.IsWhiteSpace(character))

            {

                capitaliseNext = true;

            }

            else if (capitaliseNext)

            {

                capitaliseNext = false;

                characterToAppend = Char.ToUpper(character);

            }

            stringBuilder.Append(characterToAppend);

        }

        return stringBuilder.ToString();

    }

}