private void button1_Click(object sender, EventArgs e)
        {
            string strcon = "server=lbwin7.\\SQLEXPRESS;uid=sa;pwd=sa;database=StuInfo";
            SqlConnection con = new SqlConnection(strcon);
            con.Open();
            string sql = "select * from T_Student";
            SqlDataAdapter sda = new SqlDataAdapter(sql, con);
            DataSet ds = new DataSet();
            sda.Fill(ds, "el");
            dataGridView1.DataSource = ds.Tables ["el"];           
            con.Close();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            string strcon = "server=lbwin7.\\SQLEXPRESS;uid=sa;pwd=sa;database=StuInfo";
            SqlConnection con = new SqlConnection(strcon);
            con.Open();
            string sql = "update T_Student set 姓名='" + textBox1.Text + "' where 编号='" + textBox1.Text + "'";
            SqlCommand sqlcmd = new SqlCommand(sql, con);
            sqlcmd.ExecuteNonQuery();

            con.Close();
        }

        private void button2_Click_1(object sender, EventArgs e)
        {
            string strcon = "server=lbwin7.\\SQLEXPRESS;uid=sa;pwd=sa;database=StuInfo";
            SqlConnection con = new SqlConnection(strcon);
            con.Open();
        }
    }
}
线程 0x1d40 已退出，返回值为 0 (0x0)。
线程 0x17f8 已退出，返回值为 0 (0x0)。
线程 0x1544 已退出，返回值为 0 (0x0)。
“SQL.vshost.exe”(托管): 已加载“C:\Windows\assembly\GAC_MSIL\System.Windows.Forms.resources\2.0.0.0_zh-CHS_b77a5c561934e089\System.Windows.Forms.resources.dll”，未加载符号。
“SQL.vshost.exe”(托管): 已加载“C:\Windows\assembly\GAC_MSIL\System.Data.resources\2.0.0.0_zh-CHS_b77a5c561934e089\System.Data.resources.dll”，未加载符号。
在 System.Data.SqlClient.SqlException 中第一次偶然出现的“System.Data.dll”类型的0异常

运行时这个两个错误怎么搞..

兄弟！button1_Click你用的时SqlDataAdapter数据适配器和DataSet ，是离线式数据库连接。不用con.open()和con.close()的。打开和关闭数据库都是由SqlDataAdapter数据适配器自动完成的。
你试试下面的代码：
private void button1_Click(object sender, EventArgs e)
        {
            string strcon = "server=lbwin7.\\SQLEXPRESS;uid=sa;pwd=sa;database=StuInfo";
            SqlConnection con = new SqlConnection(strcon);
            string sql = "select * from T_Student";
            SqlDataAdapter sda = new SqlDataAdapter(sql, con);
            DataSet ds = new DataSet();
            sda.Fill(ds, "el");
            dataGridView1.DataSource = ds.Tables ["el"];           
            dataGridView1.DataBind();     
   }

数据更新的语句多了个双引号