{“已经有与此命令相关联的打开的DataReader，必须首先关闭它。”}

Question

There is already an open DataReader associated with this Command which must be closed first.

应用程序崩溃

internal void database_mailing_address(string dataBasePath, string to_address, string from_address)
        {
            //  MessageBox.Show(dataBasePath+ to_address+ to_address+ from_address);
            //    OleDbConnection con = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + @dataBasePath + "\\qrcodedetails.mdb");
            //try {
                if (File.Exists(@dataBasePath))
                {
                    //   OleDbConnection con = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\Gunjan\\Documents\\Visual Studio 2015\\Projects\\MultiLabel\\qrcodedetails.mdb");

                    OleDbConnection con = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + @dataBasePath);
                    OleDbCommand cmd = con.CreateCommand();
                    con.Open();


                cmd.CommandText = "select count(*) from mailing_address where (to_address ='" + @to_address.Trim() + "') AND (from_address ='" + @from_address.Trim() + "')";


                OleDbDataReader dr = cmd.ExecuteReader();
                    if (dr.Read())
                    {
                        MessageBox.Show("Data already existed in the table");
                    cmd.CommandText = "UPDATE  mailing_address SET to_address ='" + @to_address.Trim() + "' , from_address ='" + @from_address.Trim() + "' WHERE to_address ='" + @to_address.Trim() + "' AND from_address='" + @from_address.Trim();
                    cmd.ExecuteNonQuery();

                }

                cmd.CommandText = "Insert into mailing_address(to_address,from_address)Values('"
                + to_address + "','" + from_address + "')";
                    cmd.Connection = con;
                    cmd.ExecuteNonQuery();

                    con.Close();

                }
            //}
          //  catch (Exception e)
            //{

            //}
        }