Program.cs

using System;

namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            var interceptor = default(Func<Func<DateTime>, Func<DateTime>>);
            interceptor = indirection => () =>
            {
                try
                {
                    Console.WriteLine("前処理");
                    return indirection();
                }
                finally
                {
                    Console.WriteLine("後処理");
                }
            };

            var intercepted = interceptor(() => { Console.WriteLine("本処理"); return DateTime.Now; });
            Console.WriteLine("結果: {0}", intercepted());
            // --------------------------
            // 前処理
            // 本処理
            // 後処理
            // 結果: 2014/08/15 16:09:12

            Console.ReadLine();
        }
    }
}