我的程序代码是下面这样的：
string connString = @"Data Source=.\sqlexpress;Initial Catalog=S_C_A;Integrated Security=True;Pooling=False";
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = conn.CreateCommand();
            string sql = "select * from class ";
             = sql;

            
            SqlDataAdapter adapter = new SqlDataAdapter(sql, conn);
            DataTable table = new DataTable();

            comboBox1.DataSource = table;
            adapter.Fill(table);
            comboBox1.DisplayMember = "classname";
            comboBox1.ValueMember = "ClassID";
出不来我想要的结果。请问我错在哪里！

怎么没人关注啊。先谢谢了

我换过了，没有反应，不过还是要谢谢你。

我改成这样也不行啊：
string connString = @"Data Source=.\sqlexpress;Initial Catalog=S_C_A;Integrated Security=True;Pooling=False";
            SqlConnection conn = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = conn;
            string sql = "select * from class where classname=c1";
             = sql;


            SqlDataAdapter adapter = new SqlDataAdapter(sql, conn);
            DataTable table = new DataTable("S_C_A");


            adapter.Fill(table);
            comboBox1.DataSource = table;
            comboBox1.DisplayMember = "classname";
            comboBox1.ValueMember = "ClassID";

谢谢楼上的，它提示我无法将方法组Ｒead转化为非委托型bool

我改过来了，但是还是没有反应。