using System;

public class Program

{

    public static void Main()

    {

        try {

            A();

        } catch (Exception e) {

            Console.WriteLine("throw"); 

            Console.WriteLine(e.StackTrace);

        }

        Console.WriteLine();

        try {

            A(throwEx: true);

        } catch (Exception e) {

            Console.WriteLine("throw ex");  

            Console.WriteLine(e.StackTrace);

        }       

    }

    private static void A(bool throwEx = false)

    {

        try {

            B();    

        } catch (Exception ex) {

​

            if (throwEx) {

                throw ex;   

            } else {

                throw;  

            }

        }

    }

    private static void B()

    {

        C();

    }

    private static void C() 

    {

        throw new Exception("Blah");

    }

}