Create filtered dataset from XML file?

[johnb41]

I need to create a Dataset and datatable from an XML file. The only
way I know how to make a Dataset and Datatable, is by using an Access
database as my datastore: You know, the usual thing in all the books;
an OleDbDataAdapter, with a SQL string and connection.

How can I do this using an XML file instead of an Access table? I know
I can convert an XML file straight into a Dataset. But the dataset
always contains ALL the info from the XML file. I want the dataset to
be filtered by using some sort of query.

A couple years ago I hurt my brain figuring out Xpath. Boy, i'm just
not meant to understand it! Is Xpath what I'm supposed to use?

Can anyone shed some light on this for me?

Thanks!
John

[Derek Harmon]

"johnb41" <or****@informatik.com> wrote in message news:11**********************@f14g2000cwb.googlegr oups.com...

The only way I know how to make a Dataset and Datatable, is by
using an Access database as my datastore:
Well, you can always create a DataTable programmatically,

DataTable table = new DataTable( "Orders");

Then add columns to it,

table.Columns.Add( new DataColumn( "Order", typeof(string)));
table.Columns.Add( new DataColumn( "ShipDate", typeof(DateTime)));

With the default deserialization logic, you can (to a limited extent) customize
what sorts of XML nodes these data columns are mapped from,

table.Columns[ "ShipDate"].ColumnMapping = MappingType.Attribute;

Then add rows to it,

table.Rows.Add( new object[] { "7-button mouse", new DateTime( 2005, 4, 18) } );
table.Rows.Add( new object[] { "red wagon", new DateTime( 2005, 3, 26) } );
I know I can convert an XML file straight into a Dataset. But the dataset
always contains ALL the info from the XML file. I want the dataset to
be filtered by using some sort of query.
Filtering this should be possible by writing a custom XmlTextReader that
strips out the content you don't want to pass through to DataSet.ReadXml( ).
How easy it is to write this custom XmlTextReader will vary proportionately
to the complexity of the queries you need to support. However, simple
filtration XmlTextReaders, like retrieve only the <Orders> where the
@ShipDate is within the past 30 days (and @ShipDate is an attribute
on Orders) are relatively simple to write.
A couple years ago I hurt my brain figuring out Xpath. Boy, i'm just
not meant to understand it! Is Xpath what I'm supposed to use?

If XPath causes you injury, then an XML approach to the problem
probably isn't your course of least resistance. Have you considered
loading all of the XML into the DataSet and then using a Row Filter
to strip out rows you don't want in a more SQL-like notation, for
instance,

DataSet dataSet1 = new DataSet( "Fulfillment");
dataSet1.Tables.Add( table);

DataView view = dataSet1.DefaultViewManager.CreateView( table);
view.RowFilter = "ShipDate > #04/01/2005#";
Derek Harmon

[johnb41]

Derek,

Thanks for your help!

XML, for me, is very difficult. I can use it in only the simplest
ways. Anything more just makes my head spin w/ all the complexity.
Your first 2 solutions just seem way too out of my reach.

The Row Filter solution looks like a good idea for me. I've done this
before and it's really easy. I can't belive i didn't consider it for
this! My only problem about it is that it's probably not very
processor efficient; you have to always load an entire XML file to a
dataset before you filter it. But in my project, it would probably not
be a very big deal.

Quick question about dataview.rowfilter: Does the SQL-like syntax
support the keyword "Between", and "and". If so, this solution should
work well for the type of queries that I need to do.

Thanks for your help!

John

[Derek Harmon]

"johnb41" <or****@informatik.com> wrote in message news:11**********************@o13g2000cwo.googlegr oups.com...

Quick question about dataview.rowfilter: Does the SQL-like syntax
support the keyword "Between", and "and".

It supports the keyword And, that allows you to emulate Between:

ColumnName between 10 and 20

can be written without Between as,

ColumnName >= 10 and ColumnName <= 20

which works fine as a row filter.

The documentation on the expression syntax is tucked away in a far
corner of the SDK, look for the help page under the .NET Frame-
work's "Class Reference" section, "System.Data" namespace,
"DataColumn" class, "Expression" property.
Derek Harmon

[johnb41]

Thanks Derek for all your help!

John