Wallpaper Generator

A nice WPF application that creates a wallpaper based on a photo folder.

Download the application from here.

FlowDocument and multiple threads

Recently, I try to use the FlowDocumentScrollViewer to display FlowDocument's. So I create WPF window application that creates and displays flow documents with FlowDocumentScrollViewer.





The refresh button clears the contents of the documentPanel, and creates and displays a random number of flow documents.





This works as expected and creates a random number of flow documents on window.
My next step is to make this work in asynchronous manner. How is that possible? Enter DispatcherObject and WPF Threading model.
The basic technique is to use the Dispatcher methods and delegates to do the heavy operations in a different thread.
To demonstrate this, I create a new "Refresh Async" button and modify the flow document creation to include a 5 sec Sleep.
The next step is to add the delegate and dispatcher calls. The refresh async button handler uses the Dispatcher to asynchronously call the GenerateAndShowFlowDocumentHandler method which creates and displays the flow document.







This also works fine.

The next step is to create the FlowDocument in a separete thread and use the main UI thread for UI update.





When I try this I get exceptions!.








To resolve this issue, I should serialize the FlowDocument as Memory stream since FlowDocument's seems that they can’t serialize themselves on different threads.
Add the following before passing the flow document.









And to the handler :





And it works great!!

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More on Vista's File Copy

Guess how much time it will take to extract a zipped file of about 5MB to a disk using Vista's extract feature?

How to port SQL Server OPENXML to Oracle PL/SQL

If you want to port code that contain OPENXML calls from SQL Server to Oracle, you will find that there is no such call. OPENXML works with sp_xml_preparedocument and xp_xml_removedocument calls to produce (among other things) a relational table based on XML document.



In my case, I use the XML document to pass an array of primary keys, use them as a filter for a table and join and return them.



For example suppose an application based on SQL Server TSQL has:

A table "BRANDS" contain a BRAND_ID (INT) and a TITLE (VARCHAR)

such as:

BRAND_ID TITLE

1 Nokia

2 Siemens

3 Other

4 IBM

5 HP



A stored procedure GET_BRAND_LIST as:

CREATE PROCEDURE dbo.GET_BRAND_LIST(@IDLIST NTEXT )

AS

DECLARE @hDoc int

EXEC sp_xml_preparedocument @hDoc OUTPUT, @IDLIST


SELECT BRAND_ID, TITLE FROM BRANDS

INNER JOIN OPENXML (@hDoc, '/s/k',2) WITH (I int) AS ResultSet

ON BRANDS.BRAND_ID = ResultSet.I



EXEC sp_xml_removedocument @hDoc

RETURN



GO



And an XML input similar to:


where:

• s is the root element




• k specifies a primary key and




• I the value of the primary key

such as:




calling GET_BRAND_LIST will return the brands with BRAND_ID equal to 1, 3 and 4.





Here is how to do the same in Oracle:

• Use CBLOB instead on NTEXT to pass the XML value.




• Use XMLType instead on sp_xml_preparedocument and sp_xml_removedocument calls.




• Use XMLSequence to convert and create a temporary table filled with the primary keys.




• Use EXTRACT to get the primary key value to perform the Join.

The complete Oracle code:
PROCEDURE GET_BRAND_LIST (cur_OUT OUT T_CURSOR, pIDLIST CLOB)
IS
anXmlType XmlType;
V_CURSOR T_CURSOR;
BEGIN
anXmlType := XmlType(pIDLIST);
OPEN V_CURSOR FOR
SELECT BRANDS.BRAND_ID, BRANDS.TITLE
FROM BRANDS,
table(XMLSequence(extract(anXMLType, '/s/k/*'))) ResultSet
WHERE BRANDS.BRAND_ID = TO_NUMBER(EXTRACT(value(ResultSet), 'I/text()'));



cur_OUT := V_CURSOR;
END;

Vista and File Copy