class Balance : DbConnection
        {
            public string bal { set; get; }
            public bool Load_Balance()
            {
                connectDb.Open();
                SqlDataReader rd;
                bool check = false;
                using (var cmd = new SqlCommand())
                {
                    cmd.CommandText = "SELECT * Student WHERE Balance=@bal";
                    cmd.CommandType = CommandType.Text;
                    cmd.Connection = connectDb;
                    cmd.Parameters.Add("@bal", SqlDbType.VarChar).Value = bal;
                    rd = cmd.ExecuteReader();
                    while (rd.Read())
                    {
                        check = true;
                    }
                    connectDb.Close();
                }
                return check;
            }
 
 
 
rd shows error bcz it doesn't exist here.
How can I fix it?
I have a connection class(DbConnection) and wanted to display value from database in another form. 
 
public void verify_bal()
        {
            Balance Bal = new Balance();
            bool verify = Bal.Load_Balance();
            if (verify == true)
            {
                txtBucks.Text = rd.GetValue(5).ToString;
            }
            else
            {
                MessageBox.Show("No!!");
            }
       
        }