Search and print console data from a .txt in C #

Hello :) Well it is a simple program in which a .txt is handled, the program has the option to enter data, print them and search ....

My problem is in the third part: Search, the data that is saved in the txt are: Password, Name and Position as follows:

  

123
Carlos Dayan Rodriguez Perez
Administrator
  -Espacio-
234
Diego Antonio Rodriguez Perez
Programmer
  -Spacio
456
Juan Camaney
Tester
  -Spacio

Notice what it says -Spa- with that indicated that instead of a line break emptied every one that ends a "record" there is a space, it is because of this ......

The code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace Programa1_Agenda
{
    class Program
    {
        static StreamReader Leer;
        static StreamWriter Escribir;

        static void Main(string[] args)
        {
            int Op;
            int op_1 = 0;
            do
            {
                Console.Clear();
                Console.WriteLine("AGENDA 2018\n\n");
                Console.WriteLine("1) Ingresar datos\n2) Mostrar datos\n3) Buscar persona\n4) Salir\n\nTu opcion: ");
                Op = int.Parse(Console.ReadLine());

                if (Op == 1)
                {
                    do
                    {
                        int DUI;
                        string nombre;
                        string puesto;
                        Console.Clear();
                        Console.WriteLine("Escribir un nuevo registro\n\n");
                        Escribir = new StreamWriter("Archivo_Agenda.txt", true);
                        //INGRESA DATOS
                        Console.Write("\n* Ingresar nueva clave DUI (3 Digitos enteros): ");
                        DUI = int.Parse(Console.ReadLine());
                        Escribir.WriteLine(DUI);
                        Console.Write("\n* Ingresar nombre completo: ");
                        nombre = Console.ReadLine();
                        Escribir.WriteLine(nombre);
                        Console.Write("\n* Ingresar puesto: ");
                        puesto = Console.ReadLine();
                        Escribir.WriteLine(puesto);
                        Console.WriteLine("\n\n");
                        String Cadena = Console.ReadLine();
                        Escribir.WriteLine(Cadena);
                        Escribir.Close();

                        Console.WriteLine("El registro se ha creado exitosamente.\n\n5) Regresar al menu principal\n6) Ingresar un nuevo usuario");
                        Console.Write("\nTu opcion: ");
                        op_1 = int.Parse(Console.ReadLine());
                    } while (op_1 == 6);
                }

                if (Op == 2)
                {
                    string Linea;
                    int contador = 0;
                    Console.Clear();
                    Leer = new StreamReader("Archivo_Agenda.txt", true);
                    Console.WriteLine("Mostrando todos los registros:\n\n");
                    while((Linea = Leer.ReadLine()) != null)
                    {
                        Console.WriteLine(Linea);
                        contador++;
                    }
                    Leer.Close();

                    Console.WriteLine("\nEl registro se mostro exitosamente.\n\n5) Regresar al menu principal\n");
                    Console.Write("\nTu opcion: ");
                    op_1 = int.Parse(Console.ReadLine());
                }

                if (Op == 3)
                {
                    string Linea;
                    int contador = 0;
                    string result_s;
                    Console.Clear();
                    Leer = new StreamReader("Archivo_Agenda.txt", true);
                    Console.WriteLine("Buscar registro por medio de clave DUI:\n\n");
                    Console.Write("Ingresa la clave DUI: ");
                    result_s = Console.ReadLine();
                    if((Linea = Leer.ReadLine()) == result_s)
                    {
                        do
                        {
                            Console.WriteLine(Linea);
                            contador++;
                        } while ((Linea = Leer.ReadLine()) != " ");
                    }
                    Leer.Close();

                    Console.WriteLine("\nEl registro se mostro exitosamente.\n\n5) Regresar al menu principal\n");
                    Console.Write("\nTu opcion: ");
                    op_1 = int.Parse(Console.ReadLine());
                }
                Console.ReadKey();
            } while (op_1 == 5);
        }
    }
}

What I try to do in option 3, is that by asking for the DUI key and being detected in the file, the following data will be printed on the screen until a space is found (and this is the reason why ...)

This is done if the first record is entered: 123, and prints the correct thing:

123
Carlos Dayan Rodriguez Perez
Administrator

But if I enter any of the other 2, nothing is printed ...: (

Please help, I do not know what to do xd