SqlDataReader returns invalid attempt when datareader closed- reg

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C#

private void BindReader(string storedproc,string[] param)
       {
           clear();
           reader = ppt.ParamReader(storedproc,param ); // Here searching a Branch Name and binding values in matching text box
           while (reader.Read())
           {
               lbl_ID.Text = reader["BRANCH_ID"].ToString();
               txt_Address.Text = reader["BRANCH_ADDRESS"].ToString();
               txt_Branch_Phone.Text = reader["BRANCH_PHONE"].ToString();
               txt_CST_Number.Text = reader["CST_NUMBER"].ToString();
               txt_tin_number.Text = reader["TIN_NUMBER"].ToString();
               cmb_Branch_Name.Text = reader["BRANCH_NAME"].ToString();
           }
           reader.Close();
       }

public SqlDataReader ParamReader(string sp, string[] pp)
{
    if (_connection.State == ConnectionState.Open)
    {
        _connection.Close();
    }
    _connection.ConnectionString = setConnection();
    try
    {
        _connection.Open();
        cmd = parameters(sp, pp, _connection);// Calls Parameters Method to load the Parameters in the command
        reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);

    }
    catch (Exception e)
    {
        throw new Exception(e.Message);
    }
    return reader;
}

<code>
This code is working at very first time. if I call this method again it returns error like invalid attempt when data reader is closed.
what is the reason? what should i do for this to over come this?