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  1. using System;
  2. using System.Collections;
  3. using System.Collections.Generic;
  4. using System.Linq;
  5.  
  6. namespace ConsoleApplication
  7. {
  8.     interface IReadOnlyList</*out*/ T> : IEnumerable<T>
  9.     {
  10.         int Count { get; }
  11.         T this[int index] { get; }
  12.     }
  13.  
  14.     interface IList<T> : IReadOnlyList<T>
  15.     {
  16.         new int Count { get; }//Note: new
  17.         new T this[int index] { get; set; }//Note: new
  18.         void Add(T item);
  19.     }
  20.  
  21.     class List<T> : IList<T>
  22.     {
  23.         private readonly System.Collections.Generic.IList<T> _innerList;
  24.  
  25.         public List(System.Collections.Generic.IList<T> innerList)
  26.         {
  27.             if (innerList == null) throw new ArgumentNullException("innerList");
  28.             _innerList = innerList;
  29.         }
  30.  
  31.         public int Count
  32.         {
  33.             get { return _innerList.Count; }
  34.         }
  35.  
  36.         public T this[int index]
  37.         {
  38.             get { return _innerList[index]; }
  39.             set { _innerList[index] = value; }
  40.         }
  41.  
  42.         public void Add(T item)
  43.         {
  44.             _innerList.Add(item);
  45.         }
  46.  
  47.         public IEnumerator<T> GetEnumerator()
  48.         {
  49.             return _innerList.GetEnumerator();
  50.         }
  51.  
  52.         IEnumerator IEnumerable.GetEnumerator()
  53.         {
  54.             return GetEnumerator();
  55.         }
  56.     }
  57.  
  58.     class Program
  59.     {
  60.         static void SomeMethod(IReadOnlyList<int> lst)
  61.         {
  62.             Console.WriteLine("Count from IReadOnlyList: {0}", lst.Count);
  63.             Console.WriteLine("First item from IReadOnlyList: {0}", lst[0]);
  64.  
  65.             foreach (var i in lst)
  66.                 Console.WriteLine(i);
  67.         }
  68.  
  69.         static void SomeMethodUsingReflection(object obj)
  70.         {
  71.             var iface = obj.GetType().GetInterfaces()
  72.                 .FirstOrDefault(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof (IList<>));
  73.  
  74.             if (iface != null)
  75.             {
  76.                 var countProp = iface.GetProperty("Count");
  77.                 var count = (int)countProp.GetValue(obj, null);
  78.                 Console.WriteLine("Count using reflection: {0}", count);
  79.             }
  80.         }
  81.  
  82.         static void MyMethod(IList<int> lst)
  83.         {
  84.             lst.Add(10);
  85.             lst.Add(20);
  86.             lst.Add(30);
  87.             lst[0] = 40;
  88.  
  89.             Console.WriteLine("Count from IList: {0}", lst.Count);
  90.             Console.WriteLine("First item from IList: {0}", lst[0]);
  91.  
  92.             SomeMethod(lst);
  93.             SomeMethodUsingReflection(lst);
  94.         }
  95.  
  96.         static void Main()
  97.         {
  98.             var lst = new List<int>(new[] {1, 2, 3}.ToList());
  99.             MyMethod(lst);
  100.             //Console.ReadKey();
  101.         }
  102.     }
  103. }
  104.  
Success #stdin #stdout 0.05s 37168KB
comments (?)
stdin
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Standard input is empty
stdout
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Count from IList: 6
First item from IList: 40
Count from IReadOnlyList: 6
First item from IReadOnlyList: 40
40
2
3
10
20
30
Count using reflection: 6
https://ideone.com/b4kwK
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
public

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