Presentation on using the Microsoft Sync Framework to implement a local database cache to sync with an occasionally connected SQL Server

1. Local Database Caching with the Microsoft Sync Framework
presented to NUFWon 11/10/2009
DESIGNING APPLICATIONS FOR
THE OCCASIONALLY CONNECTED
SCENARIO

2. About Me
 Work for Systemental, Inc as a Consultant
and Software Developer
 Software development to support Corporate
business process improvement since 2000
(Lean or Continuous Improvement Initiatives)
 .Net since 2004
 President, fwPASS.org
 Mfg. Eng. Technology degrees from Ball State
University

3. A case study in failure
 What could go wrong preparing this
presentation did
 Initial demo worked in minutes (after about three
minor problems)
 SQL CE debugging challenges
1. Refactor - created numerous problems
2. Test - find problems requiring schema changes
3. Repeat 1-2 ad nauseum

4. What we will cover
 What is the Microsoft Sync Framework?
 How you can use it?
 Why?
 How does it work?
 How do you implement it?
 Demo’s
 Gotcha’s, gotcha’s, and debugging

5. What is the Sync Framework
 Provider-based API for synchronizing data or
files across multiple applications, services,
and physical devices
 Included providers
 Database *
 File system
 Web – RSS/Atom

6. How can it be used?
 Server to Local
 Local to Server
 Bi-directional

7. Why?
 Why not pub/sub, log shipping, replication?
 Reliability
 Purpose
 schedule granularity
 Disconnected, hello….
 Argument: Internet is everywhere and growing
 CE vs. Express
 Encrypt or password protect the file
 Document-safe, no code stored in file
 Light 1.8Mb vs. 58Mb

8. How does it work?
 Visual Studio local database cache template
 Schema changes (couple fields and
tombstone)
 Triggers or 2008 Change data capture

9. Sync Process

10. Steps to Implement
 Add new item - local database cache
 Create database/tables to sync or modify DDL
 Sync Configuration wizard
 Configure source/target databases
 add/edit .sdf database
 add sync tables
 Generate/run scripts to adjust ddl/sync
 Generate typed dataset/table adapters (optional)
 Generate Linq2SQL or EF classes (optional)
 Set sync direction and .Synchronize

11. Demo project

12. Keyboard Encoder Module

13. Demo project details
 WPF application with a single keystroke input
F5 key
 Changing background color (green, yellow,
red) based on actual count vs. target count
 Two dispatcher timers:
1. Screen display color update (every second)
2. Db synchronization (every minute)
 WinForm SQL CE cache table viewer
 Using Repository pattern and Linq to SQL

14. Demos
 Existing SQL db, switch to CE 3.5 using
provider and connection string change
 Wizardry
 SQLMetal
 Profiler
 Server to local sync (default)
 local to server sync/bi-directional (code-
behind)

15. SQLMetal to create Linq2SQL
classes

16. Gotcha’s
 Visual Studio Linq2SQL template doesn’t support SQL CE
provider – use SQLMetal to generate, then include in project
 LINQ dbml created from MSSQL, not compatible CE
 SSMS 2005 would not open a CE 3.5 .sdf file. Need SSMS 2008
 Set sync direction if anything other than server to local
 Changing schema’s after generation – remove everything and
start over (use sql scripts to roll back)
 Insert/Update triggers not auto created?
 .sdf is re-initialized to empty and copied to bin/debug if newer
 Existing triggers on the table

17. Gotcha’s – primary key
 Primary key defined on table to cache
 auto-incrementing integer primary key,
unique identity with SQL CE db
 Some table defaults like newid() for
MSSQL Uniqueidentifer field do not
transfer to the .sdf schema definition. Set
in code <table>.id=Guid.NewGuid
 Linq can’t autogenerate guid on server.
Use id=Guid.NewGuid in code

18. Debugging SQL CE 3.5
• SSMS 2005 gives the following error when you try to connect to a SQL CE 3.5 .sdf file.
• Created a WinForm project PeekLocalCache to display data from .sdf file. Caution: make sure
you know which .sdf file the app is using (bin/debug, bin/release, project)
• SSMS 2008 – hopefully works
• Be careful re-creating the .sdf file using the local database cache configuration wizard
without deleting the records from the Server table.
I cleared out the Server table and ran for
a while on 11/2 without ex, on 11/3
cleared out the table and ran for 13
records. Changing to update server
table, works. Violation is in local cache
db

19. Switched PK to GUID from
Int64

20. Set autogen=true in dbml:
fail!

21. added id = Guid.NewGuid

22. Conflict resolution
 Sorry, not covering in Demos
 Enums – conflict types (between sync sessions)
 ClientInsertServerInsert - A new row is created with the same
primary key.
 ClientUpdateServerUpdate - The same row is updated. Most
common
 ClientUpdateServerDelete - A row is updated on the client but
was deleted on the server.
 ClientDeleteServerUpdate - A row is deleted on the client but
was updated on the server.
 ErrorsOccurred – all others
 Methods for handling
 Continue
 RetryApplyingRow
 RetryWithForceWrite

23. Resolution Policies
 Source wins
 Destination wins
 Specified replica wins
 Last writer wins
 Merge
 Log it or defer

24. References
 http://dean-o.blogspot.com/
 http://channel9.msdn.com/posts/funkyonex/Offline-Data-Synchronization-Services-in-Visual-
Studio-2008/
 http://videoworld-rong.blogspot.com/2009/10/adonet-sync-services.html
 http://social.microsoft.com/Forums/en-US/uklaunch2007ado.net/thread/0fd34e49-ae3d-4b50-
91f5-5e24d4a0b145
 http://skysigal.xact-solutions.com/Blog/tabid/427/EntryId/898/Using-LinqToSQL-with-SqlServer-
Compact.aspx
 http://download.microsoft.com/download/A/4/7/A47B7B0E-976D-4F49-B15D-
F02ADE638EBE/Compact_Express_Comparison.doc
 http://www.developer.com/net/article.php/3815506/Handling-Data-Conflicts-in-the-Microsoft-
Sync-Framework.htm
 http://www.geekzone.co.nz/JamesHip/6568
 http://code.msdn.microsoft.com/sync
 http://mattgoebel.spaces.live.com/blog/cns!DB12DAA600AD8227!182.entry?wa=wsignin1.0&sa=
84900002
 http://devlicio.us/blogs/billy_mccafferty/archive/2009/11/09/dependency-injection-101.aspx
 http://stackoverflow.com/questions/385796/sync-framework-can-i-sync-only-a-subset-of-my-
tables
 ASP.NET MVC Framework Unleashed by Stephen Walther, SAMS, ISBN 978-0-672-32998-2

25. Thank you!
 Website
 http://www.systemental.com
 Blogs
 http://dean-o.blogspot.com/
 http://practicalhoshin.blogspot.com
 Twitter
 http://www.twitter.com/deanwillson
 Email
 dean@systemental.com
 LinkedIn
 http://www.linkedin.com/in/deanwillson