通过中间代码窥探try-catch-finally本质：

class Program
    {
        static void Main(string[] args)
        {
            Program p = new Program();
            Console.WriteLine(p.Test1());
            //Console.WriteLine(p.Test2());
            Console.Read();
        }

        //结果为：3
        private TestClass Test1()
        {
            TestClass tc = new TestClass();
            try
            {
                tc.testVar = 2;
                return tc;
            }
            catch (Exception)
            {
                throw;
            }
            finally
            {
                tc.testVar = 3;
            }
        }

        //结果为：2
        private int Test2()
        {
            int test = 1;
            try
            {
                test = 2;
                return test;
            }
            catch (Exception)
            {
                throw;
            }
            finally
            {
                test = 3;
            }
        }

    }

    class TestClass
    {
        public int testVar = 111;

        public override string ToString()
        {
            return testVar.ToString();
        }
    }

调用方法Test2，try中return时，已经将返回值保存在中间代码的本地变量中，而不再是源码中变量test，所以finally的操作是无效的。其中间代码为：

try-catch-finally