My name
is
Jon Skeet

C# convert value of variable to variable

class Program
{
    struct St_test
    {
        public string f_name;
        public string l_name;
        public int age;
        public string email;
    }
    static void proced(int number)
    {
        St_test s = new St_test();
        Console.WriteLine("Enter the first name :");
        s.f_name = Console.ReadLine();
        Console.WriteLine("Enter the last name :");
        s.l_name = Console.ReadLine();
    agee:
        Console.WriteLine("Enter the age :");
        try { s.age = int.Parse(Console.ReadLine()); }
        catch { Console.WriteLine("You enterd viod age"); goto agee; }
        Console.WriteLine("Enter the e_mail :");
        s.email = Console.ReadLine();
    }
    static void Main(string[] args)
    {
        int num;
        nume:
        Console.WriteLine("enter the count of people you would like to store");
        try {  num = int.Parse(Console.ReadLine()); }
        catch { Console.WriteLine("you enterd void number"); goto nume; }
        for (int i = 0;  i < num;  i++)
        {
            proced(num);
        }

I want to input many of (S) to every number (num) of people.

How to repeat the procedure (proced) and every repeat the (s) variable has new name.

If I write in the procedure (proced) the next :

string r = "s" + number;

how to convert the resulted string (r) to variable to use it instead of (s) variable for each loop

You can't (easily, anyway) access variables by name like that - but there's a much better solution, which is to create a collection of some kind - an array or a list, for example.

I would suggest:

Changing your St_test struct:
- Make it a non-nested type
- Give it a clearer name (e.g. Person)
- Make it a class
- Don't expose fields - expose properties
- Potentially make it immutable, taking all the values in the constructor
Changing your proced method:
- Make it return a new Person
- Change the name to follow .NET naming conventions
- Stop using goto
- Factor out the "request an integer from the user" into a method
Changing your Main method:
- Create a List<Person>
- Repeatedly call what used to be called proced. but add the return value into the list

You'll end up with code something like this - but don't blindly copy it. Make sure you understand everything that's happening here.

using System;
using System.Collections.Generic;

public sealed class Person
{
    public string FirstName { get; }
    public string LastName { get; }
    public int Age { get; }
    public string Email { get; }

    public Person(string firstName, string lastName, int age, string email)
    {
        // TODO: Validation
        FirstName = firstName;
        LastName = lastName;
        Age = age;
        Email = email;
    }
}

public class Test
{
    private static Person CreatePersonFromUserInput()
    {
        Console.WriteLine("Enter the first name:");
        string firstName = Console.ReadLine();
        Console.WriteLine("Enter the last name:");
        string lastName = Console.ReadLine();
        Console.WriteLine("Enter the age:");
        int age = RequestInt32();
        Console.WriteLine("Enter the email address:");
        string email = Console.ReadLine();
        return new Person(firstName, lastName, age, email);
    }        

    private static int RequestInt32()
    {
        string text = Console.ReadLine();
        int ret;
        while (!int.TryParse(text, out ret))
        {
            Console.WriteLine("Invalid value. Please try again.");
            text = Console.ReadLine();
        }
        return ret;
    }

    private static void Main()
    {
        Console.WriteLine("Enter the count of people you would like to store:");
        int count = RequestInt32();
        List<Person> people = new List<Person>();
        for (int i = 0; i < count; i++)
        {
            people.Add(CreatePersonFromUserInput());
        }
        // Just to show them...
        foreach (Person person in people)
        {
            Console.WriteLine(
                $"First: {person.FirstName}; Last: {person.LastName}; Age: {person.Age}; Email: {person.Email}");
        }
    }

}

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