using System;

public class Program

{

    private const string SeparatorObservations = ". ";

    public static void Main()

    {

        string memoText = "Ola\\sNão sei\tpois é\r\nPois pois" + System.Environment.NewLine + "Sim sim";

        memoText = memoText.Replace("\r\n", SeparatorObservations).Replace("\n\r", SeparatorObservations).Replace("\n", SeparatorObservations).Replace("\r", SeparatorObservations).Replace("\\s", SeparatorObservations).Replace("\t", SeparatorObservations).Replace("\\w", SeparatorObservations).Replace(System.Environment.NewLine, SeparatorObservations);

        Console.WriteLine(memoText);

    }

}