static void Main(string[] args)
        {

            var asm = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName("foo"), System.Reflection.Emit.AssemblyBuilderAccess.RunAndSave);

            var mod = asm.DefineDynamicModule("mymod", true);
            var type = mod.DefineType("baz", TypeAttributes.Public);
            var meth = type.DefineMethod("go", MethodAttributes.Public | MethodAttributes.Static);

            var sdi = Expression.SymbolDocument("TestDebug.cs");

            var di = Expression.DebugInfo(sdi, 2, 2, 2, 12);
            var gen = DebugInfoGenerator.CreatePdbGenerator();


            var exp = Expression.Divide(Expression.Constant(2), Expression.Subtract(Expression.Constant(4), Expression.Constant(4)));
            var block = Expression.Block(di, exp);

            Expression.Lambda(block, new ParameterExpression[0]).CompileToMethod(meth, gen);

            var newtype = type.CreateType();
            asm.Save("tmp.dll");
            newtype.GetMethod("go").Invoke(null, new object[0]);
            Console.WriteLine(" ");
        }

Expression defaultExpr = Expression.Default(
                            typeof(byte)
                        );

// 显示表达式
Console.WriteLine(defaultExpr.ToString());

// 创建表达式树，并执行
Console.WriteLine(
    Expression.Lambda<Func<byte>>(defaultExpr).Compile()());

// 显示结果:
//
// default(Byte)
// 0