Re: Convert.ToDateTime

Simon,

a) Writing rdr.GetValue(15) is the same as writing rdr[15] - at runtime,
this may be a string, a DateTime or an int, but at compile time you have an
Object, and you will need the cast (or the conversion) in order for the code
to compile.

b) If you know that the 16th field is a DateTime, you can use
rdr.GetDateTime(15) which returns directly a DateTime (no cast or conversion
necessary).

c) Does your stored procedure produce in the 16th field a SQL Server
DATETIME, or a string which represents a date (and/or a time)? If it is a
string, then the cast to (DateTime) will fail (because the object is a
string, not a DateTime); the call to Convert.ToDateTime() will succeed,
provided that the string really contains the representation of a date/time.

d) Regarding the Int16, if the SP returns a small int the following code:

Int16 varI = rdr.GetInt16(10);

should work.

In general, when using data readers I prefer to rely on the specific methods
(GetInt16, GetDateTime, etc.) whenever I know the structure of the data at
hand. Only if writing some kind of "generic" read I use GetValue():

Regarding the Convert class, I avoid using it and generally succeed on that.
It reminds me of the times of VB6 and the abuse of conversions between
types. But that's only a personal opinion.

Regards - Octavio

"simon" <simon.zupan@xxxxxxxx> escribió en el mensaje
news:EctJe.1200$cE1.177303@xxxxxxxxxxxxxxxx
> Octavio,
>
> thank you for your answer.
>
> When I use =(DateTime) rdr.GetValue(15), it's not always the right result.
> For example: If my stored procedure returns time: '14:20:00' then this
> cast will return error.
> If I use convert then it returns me dateTime format.
>
> Another example:
>
> My stored procedure returns small int for example 0.
>
> If I use:
>
> int16 varI;
>
> varI=(int16)rdr.GetValue(10) I get an error.
>
> If I use:
>
> varI=convert.toInt16(rdr.GetValue(10)) then it works.
>
> So, I decided that I use everywhere convert function, unless at string
> data.
>
> Do you know maybe, why this difference?
>
> Regards,S
>
>
> "Octavio Hernandez" <dotnet@xxxxxxxxxxxx> wrote in message
> news:eOI1CF4mFHA.1968@xxxxxxxxxxxxxxxxxxxxxxx
>> Simon,
>>
>> I think you should use:
>>
>> tsEndTime = rdr.GetDateTime(15); // no cast or conversion necessary
>>
>> Of the two versions you mention, the first
>>
>> tsEndTime=(DateTime) rdr.GetValue(15);
>>
>> is more efficient, as the cast does not incur the penalty of the
>> (unnecessary) call to Convert.ToDateTime in the second version.
>>
>> Regards - Octavio
>>
>>
>> "simon" <simon.zupan@xxxxxxxx> escribió en el mensaje
>> news:n_rJe.1197$cE1.177141@xxxxxxxxxxxxxxxx
>>>I have datetime variable:
>>>
>>> Datetime tsEndTime;
>>>
>>> Should I use (DateTime):
>>> tsEndTime=(DateTime)rdr.GetValue(15)
>>>
>>> or is better to use:
>>>
>>> tsEndTime=Convert.ToDateTime(rdr.GetValue(15))
>>>
>>> What is the difference?
>>>
>>> Thanks,S
>>>
>>>
>>
>>
>
>


.

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