public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            departmentComboBox.DataSource = LoadDepartmentData();    //该句执行完为什么跳转到departmentComboBox_SelectedIndexChanged()????????
            departmentComboBox.ValueMember = "DepartmentID";
            departmentComboBox.DisplayMember = "Name";
        }

        private DataView LoadDepartmentData()
        {
            string sqlConnectionString = @"Data Source=.\SQLEXPRESS;Integrated Security=SSPI;Initial Catalog=AdventureWorks;";
            string sqlSelect = "select DepartmentID,Name from HumanResources.Department";
            SqlDataAdapter da = new SqlDataAdapter(sqlSelect, sqlConnectionString);
            DataTable dt = new DataTable();
            da.Fill(dt);
            return dt.DefaultView;
        }

        private void departmentComboBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            string message = "Selected:[" + departmentComboBox.SelectedValue + "]" + ((DataRowView)departmentComboBox.Items[departmentComboBox.SelectedIndex])["Name"];
            MessageBox.Show(message);
        }
    }

载入数据源啊

纠结了！自己想错了，本来就应该会执行departmentComboBox_SelectedIndexChanged(object sender, EventArgs e)的，这应该是进行了数据绑定的设置所触发的。本来还想为什么在调试的时候出现了突然的跳转，却找不到跳转的理由。花了好几个小时，不过失败中得经验嘛