MethodInfo writeInt = typeof(Console).GetMethod("Write", BindingFlags.Static | BindingFlags.Public, null, new Type[] { typeof(int) }, null);//获取Write方法

            Expression expResult = Expression.Block(

                new[] { iParameter, jParameter, rParameter },

                Expression.Assign(iParameter, Expression.Constant(1)),//为i赋初始值,类似于i=1;

                Expression.Loop(Expression.Block(//此处开始外部循环,表达式只能实现while循环,不能实现for循环

                Expression.IfThenElse(Expression.LessThanOrEqual(iParameter, Expression.Constant(9)),//定义执行的条件,类似于if(i<=9){

                                                                                                     //外部if为真的时候执行以下代码

                  Expression.Block(

                    Expression.Assign(jParameter, Expression.Constant(1)),//为j赋初始值,类似于j=1;

                    Expression.Loop(Expression.Block(//此处开始内部循环

                        Expression.IfThenElse(Expression.LessThanOrEqual(jParameter, iParameter),//定义执行的条件,类似于if(j<=i){

                                                                                                 //内部if为真的时候执行以下代码