Naive Database Question

[Keith Rebello]

I use VB.Net in VS2005 and rarely use databases.

I have a database to which I open a connection in my application (using
ADO). Once I have the connection, I loop through each table in the database
using a command string ("Select * from .) and a DataAdapter to populate a
DataSet. I then close the connection.

If I understand this correctly, I now have a copy of the database in memory.
I cannot seem to find a way to query this DataSet to limit the rows and
columns that I want to see in my DataGridView. Using
DataSet.Tables.Select( , ) I can limit the number of rows based on a
criterion, but cannot seem to limit the number of columns.

Am I trying to do something that is not possible? If it is possible, please
offer some suggestions. Or, do I have to re-open the connection and
re-query the original database?

Keith Rebello.

[Steve Gerrard]

Keith Rebello wrote:

I use VB.Net in VS2005 and rarely use databases.

I have a database to which I open a connection in my application
(using ADO). Once I have the connection, I loop through each table
in the database using a command string ("Select * from .) and a
DataAdapter to populate a DataSet. I then close the connection.

If I understand this correctly, I now have a copy of the database in
memory. I cannot seem to find a way to query this DataSet to limit
the rows and columns that I want to see in my DataGridView. Using
DataSet.Tables.Select( , ) I can limit the number of rows based on a
criterion, but cannot seem to limit the number of columns.

Am I trying to do something that is not possible? If it is possible,
please offer some suggestions. Or, do I have to re-open the
connection and re-query the original database?

Normally you would just set the datagridview to display the columns of interest,
regardless of how many columns are actually in the datarows you are using as a
datasource.

[Patrice]

Windows or web application ? In both case you can explicitely define which
columns you want to see (see the Columns collection).

Anyway, this is really not how a DataSet should be used. See this rather as
a "cache" rather than a "copy". The idea is rather to keep around the rows
the user needs at a given time and to move them back and forth in the
dataset or to the db as needed, note to copy the whole db...

--
Patrice

"Keith Rebello" <kr******@corefundamentals.coma écrit dans le message de
groupe de discussion : YM*************@newsfe24.lga...

I use VB.Net in VS2005 and rarely use databases.

I have a database to which I open a connection in my application (using
ADO). Once I have the connection, I loop through each table in the
database using a command string ("Select * from .) and a DataAdapter to
populate a DataSet. I then close the connection.

If I understand this correctly, I now have a copy of the database in
memory. I cannot seem to find a way to query this DataSet to limit the
rows and columns that I want to see in my DataGridView. Using
DataSet.Tables.Select( , ) I can limit the number of rows based on a
criterion, but cannot seem to limit the number of columns.

Am I trying to do something that is not possible? If it is possible,
please offer some suggestions. Or, do I have to re-open the connection
and re-query the original database?

Keith Rebello.

[Keith Rebello]

Thanks Steve.

The problem I have is that the DataGridView will have a different number of
columns and column header names dependent on which table in the dataset I
wish to query. That is why it would be nice to be able to query the DataSet
on a table-by-table basis and have the DataGridView display only pertinent
information.

Keith Rebello

"Steve Gerrard" <my********@comcast.netwrote in message
news:OI******************************@comcast.com. ..

Keith Rebello wrote:

>I use VB.Net in VS2005 and rarely use databases.

I have a database to which I open a connection in my application
(using ADO). Once I have the connection, I loop through each table
in the database using a command string ("Select * from .) and a
DataAdapter to populate a DataSet. I then close the connection.

If I understand this correctly, I now have a copy of the database in
memory. I cannot seem to find a way to query this DataSet to limit
the rows and columns that I want to see in my DataGridView. Using
DataSet.Tables.Select( , ) I can limit the number of rows based on a
criterion, but cannot seem to limit the number of columns.

Am I trying to do something that is not possible? If it is possible,
please offer some suggestions. Or, do I have to re-open the
connection and re-query the original database?

Normally you would just set the datagridview to display the columns of
interest, regardless of how many columns are actually in the datarows you
are using as a datasource.

[Keith Rebello]

Thanks Patrice. From your post, it makes sense for me to re-connect to and
re-query the database.
For completeness, it is a Windows application and the database is small in
size and is only a small component of the application.

Keith Rebello.
"Patrice" <http://www.chez.com/scribe/wrote in message
news:F4**********************************@microsof t.com...

Windows or web application ? In both case you can explicitely define which
columns you want to see (see the Columns collection).

Anyway, this is really not how a DataSet should be used. See this rather
as a "cache" rather than a "copy". The idea is rather to keep around the
rows the user needs at a given time and to move them back and forth in the
dataset or to the db as needed, note to copy the whole db...

--
Patrice

"Keith Rebello" <kr******@corefundamentals.coma écrit dans le message de
groupe de discussion : YM*************@newsfe24.lga...

>I use VB.Net in VS2005 and rarely use databases.

I have a database to which I open a connection in my application (using
ADO). Once I have the connection, I loop through each table in the
database using a command string ("Select * from .) and a DataAdapter to
populate a DataSet. I then close the connection.

If I understand this correctly, I now have a copy of the database in
memory. I cannot seem to find a way to query this DataSet to limit the
rows and columns that I want to see in my DataGridView. Using
DataSet.Tables.Select( , ) I can limit the number of rows based on a
criterion, but cannot seem to limit the number of columns.

Am I trying to do something that is not possible? If it is possible,
please offer some suggestions. Or, do I have to re-open the connection
and re-query the original database?

Keith Rebello.

[Steve Gerrard]

Keith Rebello wrote:

>
The problem I have is that the DataGridView will have a different
number of columns and column header names dependent on which table in
the dataset I wish to query. That is why it would be nice to be able
to query the DataSet on a table-by-table basis and have the
DataGridView display only pertinent information.

If you like the auto-generated columns, it should not be hard to loop through
the columns collection after binding a different datasource, and setting visible
to false for the columns you don't want to see - or removing them, for that
matter.

Or you can take control outright, and set AutoGenerateColumns to false. Then
when you change datasource, clear the columns and setup the ones you want. Don't
be fooled into thinking that AutoGenerateColumns does anything different: it
just finds the table's column collection, and loops through, setting up a grid
column for each table column. Doing it yourself gives you a much finer level of
control on a number of properties, such as the header text and format, as well
as control over which columns to show.