namespace WindowsFormsApplication1{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)        {            int year = Convert.ToInt32(comboBox1.Text);//定义一个变量，用来记录当前选择的年份            string strtext = "";//记录所选年份对应的属相；            switch(year%12)            {                case 4: strtext = "鼠"; break;                case 5: strtext = "牛"; break;                case 6: strtext = "虎"; break;                case 7: strtext = "兔"; break;                case 0: strtext = "猴"; break;            }            foreach (System.Windows.Forms.RadioButton rbtn in groupBox1.Controls)//循环遍历groupBox1容器中的单选按钮控件            {                if (rbtn.Text == strtext)                    rbtn.Checked = true;            }        }        private void Form1_Load(object sender, EventArgs e)        {            for (int i = 1990; i <= 2050; i++)                comboBox1.Items.Add(i);            comboBox1.Text = DateTime.Now.Year.ToString();//设置下拉列表的默认值为当前年份        }            }}

下面这个图里面有窗体里面用到的东西，可以多看下这个文件

下面的与上面的无关：
using System.Windows.Controls;要使用这个命名空间就要加下面选中的那个