using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;

public class Program {
    static void Main(string[] args)
    {
        object x = 2;
        var a = new A();
    	a.Val = x;
    	a.array = new A[3] { a, new A() { Val = "a"}, null};
    
    
        var b = new A();
        b.Val = x;
    	b.array = new A[3] { b, new A() { Val = "a"}, null};
        
        a.array[2] = b;
        b.array[2] = b;
    	
    	Console.WriteLine(string.Join("\n", FindStringValues(a).ToArray()));
    }
    
    public class A {
    	public A[] array {get;set;}
    	public object Val {get;set;}
    }
    
    private static IEnumerable<string> FindStringValues(object obj) {
    	return _FindStringValues(obj, new List<object>());
    }
    
    private static IEnumerable<string> _FindStringValues(object obj, IList<object> visitedObjects)
    {	
        if (obj == null)
            yield break;
            
       // Console.WriteLine(string.Join("; ", visitedObjects.Select(i => i.ToString()).ToArray()));
        if (visitedObjects.Any(item => Object.ReferenceEquals(item, obj)))
            yield break;
            
        if (!(obj is string))
            visitedObjects.Add(obj);
        
        Type type = obj.GetType();
        
        if (type == typeof(string)) {
			yield return (obj).ToString();
            yield break;
		}
        
        if (typeof(IEnumerable).IsAssignableFrom(type))
		{
			var array = obj as IEnumerable;
			foreach (var item in array)
				foreach (var str in _FindStringValues(item, visitedObjects))
					yield return str;
                    
            yield break;
		}
		
        if (type.IsClass)
		{
			FieldInfo[] fields = type.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
			foreach (FieldInfo field in fields)
			{
				object item = field.GetValue(obj);
				
                if (item == null)
					continue;
                    
                    
				foreach (var str in _FindStringValues(item, visitedObjects))
					yield return str;
			}
            
            yield break;
		}    	
    }
}