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

public class Test
{
	private static Expression<Func<T,TResult>> Unbox<T,TResult>(Expression<Func<T,object>> original) {
		return Expression.Lambda<Func<T,TResult>>(
            Expression.Convert(original.Body, typeof(TResult))
        ,   original.Parameters
        );
	}
	
	public static void Main() {
		Expression<Func<int,object>> f1 = i => i*i;
		Expression<Func<int,int>> f2 = Unbox<int,int>(f1);
		Func<int,int> f = f2.Compile();
		Console.WriteLine("Result 2 times 2 is {0}", f(2));
	}
}