(上一条)--要先定义i的变量;
if(i>0 )
            {
                i--;
                textBox1.Text=//写自己想要付的值.........              
               textBox2.Text =..........
               textBox3.Text= ..........              
              comboBox1.Text=...........;
            }
            if(i<n-1 )
            {
                i++;
                此处代码如上           
             }