onlyString.cs

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;

namespace OnlyString
{

    public static class here 
    {
        public static void start()
        {
        	IQuestion q1=new stringQuestion();
		q1.setinfo("عاصمة العراق","بغداد");
		IQuestion q2=new mathDblQuestion();
		q2.setinfo("5/2",((double)5/2).ToString());
		IQuestion q3=new mathIntQuestion();
		q3.setinfo("5+6",(5+6).ToString());
		
		bool f;
		Console.WriteLine("start");
		while(true)
		{
			f=askandcheck(q1);
			if(!f) break;
			f=askandcheck(q2);
			if(!f) break;
			f=askandcheck(q3);
			if(!f) break;
		}
		Console.WriteLine("end");
		
        }
	public static void start2()
        {
        	IQuestion q1=new stringQuestion();
		q1.setinfo("عاصمة العراق","بغداد");
		IQuestion q2=new mathDblQuestion();
		q2.setinfo("5/2",((double)5/2).ToString());
		IQuestion q3=new mathIntQuestion();
		q3.setinfo("5+6",(5+6).ToString());

		// you can store all questions in array
		IQuestion[] qs=new IQuestion[]{q1,q2,q3};
		
		bool f=true;int i=0;
		Console.WriteLine("start");
		while(f)
		{
			f=askandcheck(qs[i]);
			i++;if(i==qs.Length) i=0;
		}
		Console.WriteLine("end");
		
	}
        public static bool askandcheck(IQuestion q)
        {
        	Console.WriteLine("enter !! to exit");
        	Console.Write("Q: "+q.question+" ? ");
        	string ua=Console.ReadLine();
        	if(ua=="!!") return false;
        	if(q.checkanswer(ua))
        		Console.WriteLine("good answer");
        	else
        		Console.WriteLine("bad answer");
        	Console.WriteLine();
        	return true;
        }
        
    }
    public interface IQuestion
    {
    	string question {get;}
    	string answer {get;}
    	void setinfo(string q,string s);
    	bool checkanswer(string ua);
    }
    public class stringQuestion : IQuestion
    {
    	private string _question;
    	private string _answer;
    	public string question
    		=> _question;
    	public string answer
    		=> _answer;
    	public void setinfo(string q,string a)
    	{
    		_question=q;
    		_answer=a;
    	}
    	public bool checkanswer(string ua)
    	{
    		return _answer==ua;
    	}
    }
    public class mathDblQuestion : IQuestion
    {
    	private string _question;
    	private string _answer;
    	public string question
    		=> _question;
    	public string answer
    		=> _answer;
    	public void setinfo(string q,string a)
    	{
    		_question=q;
    		_answer=a;
    	}
    	public bool checkanswer(string ua)
    	{
    		try
    		{
    			return double.Parse(_answer)==double.Parse(ua);
    		}
    		catch(Exception ex)
    		{
    			return false;
    		}
    	}
    }
    public class mathIntQuestion : IQuestion
    {
    	private string _question;
    	private string _answer;
    	public string question
    		=> _question;
    	public string answer
    		=> _answer;
    	public void setinfo(string q,string a)
    	{
    		_question=q;
    		_answer=a;
    	}
    	public bool checkanswer(string ua)
    	{
    		try
    		{
    			return int.Parse(_answer)==int.Parse(ua);
    		}
    		catch(Exception ex)
    		{
    			return false;
    		}
    	}
    }
    
}