Display value from database in textbox using c# oop

Question

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!!");

}

}