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  1. using System;
  2.  
  3. namespace Test
  4. {
  5. 	public class A 
  6. 	{
  7. 	    public string Info { get; set; }
  8. 	    /* much more data */
  9. 	}
  10.  
  11. 	public class B
  12. 	{
  13. 	    private A m_instanceOfA;
  14.  
  15. 	    public B(A a) { m_instanceOfA = a; }
  16.  
  17. 	    public string Info
  18. 	    {
  19. 	    	get { return m_instanceOfA.Info; }
  20. 	    	set { m_instanceOfA.Info = value; }
  21. 	    }
  22.  
  23. 	    // requires an instance of a private object, this establishes our pseudo-friendship
  24. 	    internal A GetInstanceOfA(C.AGetter getter) { return getter.Get(m_instanceOfA); }
  25.  
  26. 	    /* And some more data of its own*/
  27. 	}
  28.  
  29. 	public class C
  30. 	{
  31. 	    private A m_instanceOfA;
  32.  
  33. 	    private static AGetter m_AGetter; // initialized before first use; not visible outside of C
  34.  
  35. 	    // class needs to be visible to B, actual instance does not (we call b.GetInstanceOfA from C)
  36. 	    internal class AGetter
  37. 	    {
  38. 	        static AGetter() { m_AGetter = new AGetter(); } // initialize singleton
  39.  
  40. 	        private AGetter() { } // disallow instantiation except our private singleton in C
  41.  
  42. 	        public A Get(A a) { return a; } // force a NullReferenceException if calling b.GetInstanceOfA(null)
  43. 	    }
  44.  
  45. 	    static C()
  46. 	    {
  47. 	    	// ensure that m_AGetter is initialized
  48. 	    	System.Runtime.CompilerServices.RuntimeHelpers.RunClassConstructor(typeof(AGetter).TypeHandle);
  49. 	    }
  50.  
  51. 	    public C(B b)
  52. 	    {
  53. 	    	m_instanceOfA = b.GetInstanceOfA(m_AGetter);
  54. 	    }
  55.  
  56. 	    public string Info
  57. 	    {
  58. 	    	get { return m_instanceOfA.Info; }
  59. 	    	set { m_instanceOfA.Info = value; }
  60. 	    }
  61.  
  62. 	    /* And some more data of its own*/
  63. 	}
  64.  
  65. 	public class Test
  66. 	{
  67. 		public static void Main()
  68. 		{
  69. 			A a = new A();
  70. 			B b = new B(a);
  71. 			C c = new C(b);
  72. 			c.Info = "Hello World!";
  73. 			Console.WriteLine(a.Info);
  74. 		}
  75. 	}
  76. }
Success #stdin #stdout 0.01s 131648KB
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Standard input is empty
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Hello World!
https://ideone.com/gSq4ZF
language:
C# (gmcs 5.20.1)
created:
8 years ago
visibility:
secret

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