using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Replacing only characters using Regex in string C#\n");

        string sampleText = "I like .NET 4.5. This is awesome.";

        //find all characters that are letters

        Regex regex = new Regex("[a-zA-Z]");

        sampleText = regex.Replace(sampleText, "$");

        Console.WriteLine(sampleText);

    }

}