Visual C# 2010 กับ SQL Server 2008 select ข้อมูลมาแล้วเช็คยังไงครับ

sql = "SELECT user_id, password, first_name,level FROM USER_USE_PRO WHERE user_id ='"+textBox1.Text+"' AND password ='"+textBox2.Text+"'";

            sqlcmd = new SqlCommand(sql, connection);
            sqlcmd.CommandText = sql;

            da = new SqlDataAdapter(sqlcmd);
            da.SelectCommand = sqlcmd;

            ds = new DataSet();
            da.Fill(ds, "USER_USE");
 

            bindingSrc = new BindingSource();
            bindingSrc.DataSource = ds.Tables["USER_USE"];