public partial class Form1 : Form
    {
        string strCon;
        SqlConnection sqlCon;
       
        public Form1()
        {
            InitializeComponent();
        }

        private void Label1_Click(object sender, EventArgs e)
        {

        }

        private void DBConnect()
        {
            //编写数据库连接字符串
            strCon = "server = 'Dolphin-pc';database = 'scoreMIS';uid ='sa'; pwd ='******' ;";

            //新建SQL SERVER 连接
            sqlCon = new SqlConnection(strCon);
        }

        //刷新显示数据
        private void ComonDataView()
        {
            try
            {

                DBConnect();

                //创建适配器
                SqlDataAdapter da = new SqlDataAdapter("select ID as 学号, name as 姓名 , class as 班级 from students", sqlCon);

                //创建数据集
                DataSet ds = new DataSet();

                da.Fill(ds, "tablename");

                dataGridView1.DataSource = ds.Tables[0];

                cbID.DisplayMember = "学号";
                cbID.ValueMember = "学号";

                cbID.DataSource = ds.Tables[0].DefaultView;
            }
            catch (SystemException ex)
            {
                MessageBox.Show("错误：" + ex.Message, "错误提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
            }
            finally
            {
                if (sqlCon.State == ConnectionState.Open)
                {
                    sqlCon.Close();
                    sqlCon.Dispose();
                }
            }

        }

        //加载
       

        private void Form1_Load(object sender, EventArgs e)
        {
            ComonDataView();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                DBConnect();
                sqlCon.Open();
                SqlCommand cmd = new SqlCommand("insert into students values ('" + cbID.Text + "', '" + tbName.Text + "', '" + tbClass.Text + "')", sqlCon);
                cmd.ExecuteNonQuery();
                sqlCon.Close();
                ComonDataView();
            }
            catch (SystemException ex)
            {
                MessageBox.Show("错误：" + ex.Message, "错误提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {

            try
            {
                DBConnect();
                sqlCon.Open();
                SqlCommand cmd = new SqlCommand("delete from students where ID = '" + cbID.Text +"'", sqlCon);
                cmd.ExecuteNonQuery();
                sqlCon.Close();
                ComonDataView();
            }
            catch (SystemException ex)
            {
                MessageBox.Show("错误：" + ex.Message, "错误提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            try
            {
                DBConnect();
                sqlCon.Open();
                SqlCommand cmd = new SqlCommand("UPDATE students SET ID = '"+ cbID.Text + "', name = '"
                    + tbName.Text + "',class = '" + tbClass.Text + "' WHERE ID = '"+ cbID.Text + "'", sqlCon);
                cmd.ExecuteNonQuery();
                sqlCon.Close();
                ComonDataView();
            }
            catch (SystemException ex)
            {
                MessageBox.Show("错误：" + ex.Message, "错误提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
            }
        }

    }