invalid attempt to call metadata when reader is closed in asp.net

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C#3.5

Here I can't find out the Error. Plz help me .


Here Is My .cs Code page

protected void grvAuthor_SelectedIndexChanged(object sender, EventArgs e)
   {
       Label lblID = (Label)grvAuthor.Rows[grvAuthor.SelectedIndex].FindControl("Label1");
       SqlDataReader dr = helperclass.fillAllData("Select * from RACKDETAILS where RACKID='"+lblID.Text+"'");
       if (dr.Read())
       {
           txtRackId.Text = dr["RACKID"].ToString();
           txtRackName.Text = dr["RACKNAME"].ToString();
           txtRackRemarks.Text = dr["REMARKS"].ToString();
       }
       else
       {
           ScriptManager.RegisterStartupScript(this.Page, typeof(string), "", "alert('Error in Connection...');", true);
       }

   }

Here My .cs Class Code

public static SqlDataReader fillAllData(string query)
    {
        SqlDataReader dr = null;
        using (SqlConnection con = new SqlConnection(helperclass.constring))
        {
            SqlCommand cmd = new SqlCommand(query, con);
            if (con.State == ConnectionState.Closed)
                con.Open();
            dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
            return dr;
            
        }
    }

Thanks in advancce.