using System;
using System.Linq;
using System.Linq.Expressions;

public class Test
{
	
	private class A
{
    private readonly int _value;

    public A(int value)
    {
        _value = value;
    }

    public int Value { get { return _value; } }
}

private class B
{
    private readonly int _value;

    private B(int value)
    {
        _value = value;
    }

    public int Value { get { return _value; } }

    public static explicit operator B(A value)
    {
        return new B(value.Value);
    }
}
	private static B ConvertFromObject(object a) {
		if (a == null) return null;
		var p = Expression.Parameter(typeof(object));
		var c1 = Expression.Convert(p, a.GetType());
		var c2 = Expression.Convert(c1, typeof(B));
		var e = (Func<object,B>)Expression.Lambda(c2, p).Compile();
		return e(a);
	}
	
	public static void Main()
	{
		object a = new A(5);
		var b = ConvertFromObject(a);
		Console.WriteLine("{0}", b.Value);
	}
}