SQLDataReader -- more questions

[Dom]

Still teaching myself about SQLDataReader and associated classes. I
have to say, the new HELP screens from MS are just about useless!!

Let's assume I have just read some records from a table into the
SQLDataReader object, r.

1. Am I right to assume that accessing the fields as r[int] is a
little faster than r[name]?

2. The elements of r are all objects. I can changes these to the
appropriate objects by upcasting, (string) r[0], or (DateTime) r[0],
etc. But how do I get a field that is an integer, or a float?

3. This isn't really about SQLDataReader, but it came up at the same
time. How do I get the number of days between 2 dates. I tried
((DateTime) r[0]).Subtract ((DateTime) r[1]), but it didn't work.

Thanks,

Dom

[sloan]

1. You get a small savings, because there is no lookup. But yes, you are
right.

2. No. You can use GetString, GetDateTime...a nd you SHOULD use
these....GetVal ue is just there as a last resort.

3. Since we don't know your query, r[0] and r[x] mean nothing to us. Put
you values into a temp variable...and then do the subtraction.
You might want to look up the TimeSpan objects as well.
If you want to see a maintainable, readable way to use GetString(
ordinalNumber )....check this blog entry:
http://sholliday.space s.live.com/Blog/cns!A68482B9628 A842A!140.entry

download the code, and look at the CustomerControl ler (or AnythingControl ler
for that matter).


"Dom" <do********@gma il.comwrote in message
news:28******** *************** ***********@v4g 2000hsf.googleg roups.com...

Still teaching myself about SQLDataReader and associated classes. I
have to say, the new HELP screens from MS are just about useless!!

Let's assume I have just read some records from a table into the
SQLDataReader object, r.

1. Am I right to assume that accessing the fields as r[int] is a
little faster than r[name]?

2. The elements of r are all objects. I can changes these to the
appropriate objects by upcasting, (string) r[0], or (DateTime) r[0],
etc. But how do I get a field that is an integer, or a float?

3. This isn't really about SQLDataReader, but it came up at the same
time. How do I get the number of days between 2 dates. I tried
((DateTime) r[0]).Subtract ((DateTime) r[1]), but it didn't work.

Thanks,

Dom

[Michael Rubinstein]

Dom,

2. The elements of r are all objects. I can changes these to the
appropriate objects by upcasting, (string) r[0], or (DateTime) r[0],
etc. But how do I get a field that is an integer, or a float?

r.GetInt32(i), r.GetFloat(i).. .

r.GetDateTime(i ) is better then casting. Checking for DbNull is highly
recommended

if (!r.IsDbNull(i) )
DateTime myDate = r.GetDateTime(i ));

3. This isn't really about SQLDataReader, but it came up at the same
time. How do I get the number of days between 2 dates. I tried
((DateTime) r[0]).Subtract ((DateTime) r[1]), but it didn't work.

System.TimeSpan tsp = r.GetDateTime(0 ) - r.GetDateTime(1 );
//or System.TimeSpan tsp = r.GetDateTime(0 ).Substract(r.G eDateTime(1));

int days = tsp.Days;

Michael

"Dom" <do********@gma il.comwrote in message
news:28******** *************** ***********@v4g 2000hsf.googleg roups.com...

Still teaching myself about SQLDataReader and associated classes. I
have to say, the new HELP screens from MS are just about useless!!

Let's assume I have just read some records from a table into the
SQLDataReader object, r.

1. Am I right to assume that accessing the fields as r[int] is a
little faster than r[name]?

2. The elements of r are all objects. I can changes these to the
appropriate objects by upcasting, (string) r[0], or (DateTime) r[0],
etc. But how do I get a field that is an integer, or a float?

3. This isn't really about SQLDataReader, but it came up at the same
time. How do I get the number of days between 2 dates. I tried
((DateTime) r[0]).Subtract ((DateTime) r[1]), but it didn't work.

Thanks,

Dom

[sloan]

One caveat.

tsp.TotalDays

There is a subtle difference between .Days and .TotalDays, fyi.
http://msdn2.microsoft.com/en-us/lib...n_members.aspx
Just an fyi....it depends on your need. I just mention it because
".Total____ _" is at the bottom of the intellisense options, and sometimes
you don't see it.


"Michael Rubinstein" <mSPAM_REMOVEr@ m®ubinstein.com wrote in message
news:5s******** *****@mid.indiv idual.net...

Dom,

>2. The elements of r are all objects. I can changes these to the
appropriate objects by upcasting, (string) r[0], or (DateTime) r[0],
etc. But how do I get a field that is an integer, or a float?

r.GetInt32(i), r.GetFloat(i).. .

r.GetDateTime(i ) is better then casting. Checking for DbNull is highly
recommended

if (!r.IsDbNull(i) )
DateTime myDate = r.GetDateTime(i ));

>3. This isn't really about SQLDataReader, but it came up at the same
time. How do I get the number of days between 2 dates. I tried
((DateTime) r[0]).Subtract ((DateTime) r[1]), but it didn't work.

System.TimeSpan tsp = r.GetDateTime(0 ) - r.GetDateTime(1 );
//or System.TimeSpan tsp = r.GetDateTime(0 ).Substract(r.G eDateTime(1));

int days = tsp.Days;

Michael

"Dom" <do********@gma il.comwrote in message
news:28******** *************** ***********@v4g 2000hsf.googleg roups.com...

>Still teaching myself about SQLDataReader and associated classes. I
have to say, the new HELP screens from MS are just about useless!!

Let's assume I have just read some records from a table into the
SQLDataReade r object, r.

1. Am I right to assume that accessing the fields as r[int] is a
little faster than r[name]?

2. The elements of r are all objects. I can changes these to the
appropriate objects by upcasting, (string) r[0], or (DateTime) r[0],
etc. But how do I get a field that is an integer, or a float?

3. This isn't really about SQLDataReader, but it came up at the same
time. How do I get the number of days between 2 dates. I tried
((DateTime) r[0]).Subtract ((DateTime) r[1]), but it didn't work.

Thanks,

Dom