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  1. using System;
  2. using System.Linq;
  3. using System.Linq.Expressions;
  4.  
  5. public class Test
  6. {
  7.  
  8. 	private class A
  9. {
  10.     private readonly int _value;
  11.  
  12.     public A(int value)
  13.     {
  14.         _value = value;
  15.     }
  16.  
  17.     public int Value { get { return _value; } }
  18. }
  19.  
  20. private class B
  21. {
  22.     private readonly int _value;
  23.  
  24.     private B(int value)
  25.     {
  26.         _value = value;
  27.     }
  28.  
  29.     public int Value { get { return _value; } }
  30.  
  31.     public static explicit operator B(A value)
  32.     {
  33.         return new B(value.Value);
  34.     }
  35. }
  36. 	private static B ConvertFromObject(object a) {
  37. 		if (a == null) return null;
  38. 		var p = Expression.Parameter(typeof(object));
  39. 		var c1 = Expression.Convert(p, a.GetType());
  40. 		var c2 = Expression.Convert(c1, typeof(B));
  41. 		var e = (Func<object,B>)Expression.Lambda(c2, p).Compile();
  42. 		return e(a);
  43. 	}
  44.  
  45. 	public static void Main()
  46. 	{
  47. 		object a = new A(5);
  48. 		var b = ConvertFromObject(a);
  49. 		Console.WriteLine("{0}", b.Value);
  50. 	}
  51. }
Success #stdin #stdout 0.14s 26168KB
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https://ideone.com/b2Vmj2
language:
C# (gmcs 5.20.1)
created:
9 years ago
visibility:
public

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