1. Windows Phone
programming: pain and
how to deal with
Nguyen Thai Son

2. Agenda
1. Image Cache - Why? What we need? How to
used?
2. LINQ - Tip and trick to improve performance

3. Image Cache - Why? What
we need? How to used?

4. 1.1 Image Cache mechanism in
WP
• Image has been cache in memory and has been
release by garbage collector
• Cache policy compliance with HTTP/1.1 Cache
Control directive
‒ Support Etag, max-age, Expires, Last-Modified …

5. 1.2 Why we need other Image Cache?
• Windows Phone OS just cache your image in one session
• Current HTTP/1.1 Cache Control directive config is not the
best
• Need control memory consume and Image life cycle

6. 1.3 What we need to Cache Image

8. Local Cache
• Organize by folder
• Used FIFO rule to roll cache

9. 1.4 How to used
• Cache every thing you can
‒ Better on Control memory
• Short cache Temporary Image – which something
like this
HTTP/1.1 302 OK
Location: /default
Cache-Control: no-store, no-cache, must-revalidate
Date: Fri, 05 Jul 2013 20:05:03 GMT
Content-Length: 0

10. How to used (cont)
• Only take what you need
• Download Image from
Network should be held as
Stack and have limit Stack size
1
2
3
4

11. How to used (cont)
• Scheduled to clean up local cache to
avoid waste on disk - event permanent
Image

12. LINQ - Tip and trick to
improve performance

13. 2.1.Existing problems with LINQ
• Write time increased when used one instance of
DataContext many time
0
50
100
150
200
250
50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000
Write time
One instance 50 item / instance 1 item / instance

14. Existing problems with LINQ (cont)
• Read time increased rapidly when amount of
record is growing
100 record 20K record
Read time (one
record)
15 ms 242 ms

15. 2.2.How to improve
• Write batch of Query
Time (ms)
Write each query (1000 query) 17866
Write batch query(1000 query) 1835

16. How to improve (cont)
• Used CompiledQuery with Query has been called
frequently
‒ Translate Linq query to SQL query => Run the query =>
Retrieve the data
100 times 3000 times
Non Compiled Query 2427 ms 101039 ms
Compiled Query 739 ms 50702 ms

17. How to improve (cont)
• Only take which Entity you need
17
20K Record
Count Full Entity 2803
Count One Entity 607