if (comboBox1.Text != "" && comboBox2.Text != "" && comboBox3.Text != "" && comboBox4.Text != "" && comboBox5.Text != "" )
            {
                SqlConnection con = DB.CreateConn();
                con.Open();
                SqlDataAdapter sda = new SqlDataAdapter("update teaching set 系部名='" + comboBox1 + "',专业名='" + comboBox2 + "',班级名='" + comboBox3 + "',where 教师名='" + comboBox4 + "',课程名='" + comboBox5 + "'", con);
                DataSet ds = new DataSet();
                sda.Fill(ds, "teaching");
                MessageBox.Show("修改保存成功！");
                dataGrid1.DataSource = DB.databind("select * from teaching", "teaching").DefaultView;
                con.Close();



    错误信息：在关键字 'where' 附近有语法错误。求高手指导，谢谢！

错误信息指向！

你要给它条件撒
不然他怎么知道更新什么呢
update table name='MM' where id=2

SqlDataAdapter sda = new SqlDataAdapter("update teaching set 系部名='" + comboBox1.text + "',专业名='" + comboBox2.text + "',班级名='" + comboBox3.text + "'where 教师名='" + comboBox4.text + "'and 课程名='" + comboBox5.text + "'", con);

看错了
你的条件不能用,  分开的