Re: Was Gamma, is just for speak

[Reggie Burnett]

Umberto Ballestrazzi wrote:
> While performances tests are running...
>
> I think that GetValue of DataReader (IDataRecord
> implementation) is used only by Framework
> (DataTable). I can't find a statement (on MSDN)
> that says that the returned type should be CLR/CTS
> compliant but if GetValue does not return a CTS
> many things stop works.
> You are right when you say that we should not
> loose dbms specific types or features (ie date
> ranges) but I think MS implementation (specifics
> calls to DataReader ie GetMySqlValue or
> GetMySqlDateTime) is not so bad...

I'm not sure you are right about things "not working" when you don't return a CTS type. I have now implemented IComparable on MySqlDateTime and am able to successfully pump a datatable full of MySqlDateTime, sort them using a dataview, and then print them out.

Now, if you are feeding a column in a typed datatable that is typed to be DateTime, then yes you would have a problem.

It's true that the docs are very vague on how non-CTS types should be handled when dealing with datasets, datatables, and data adapters.

One more item to think about. I think the connector *HAS* to work with tables that contain zero datetime values. While I will never understand why people use zero datetimes in MySQL, the fact is they do. The server will create zero datetime values if you feed it an illegal value. Since the connector has to support them, then what would happen if you attempted to update some records using a commandbuilder/dataadapter pair and the connector returned DateTime.MinValue for those values? The zero value in the database would get overwritten with 1/1/1 even though the user didn't change it. This is certainly not what we want. Some users actually use zero datetime to mean things and their apps wil break if the value is changed.

The short of this is if you have a datatable that might have zero datetime values in it, reader.GetValue() *MUST* return a MySqlDateTime. If not, the data adapter will not be able to update it successfully.

-reggie