offline network detection in microsoft silverlight 3
DESCRIPTION
Come hear how to structure Silverlight applications to support a sometimes connected scenario, and learn how to avoid the common pitfalls of implementing network detection.TRANSCRIPT
Offline Detection in SL 3 and .NET Framework
Peter SmithProgram Manager, .NET NetworkingMicrosoft Corporation
Why Offline Detection?
Silverlight now has the ability to run from the user’s desktop, just like a normal application
Sometimes when your code runs, the user will not be online
You have to detect and handle this case
The One Take-Away Point
How do you know if you are online?
1. Can you connect to your server?2. Have you validated the response?
Microsoft can help by telling you when to try again
Demonstration
A very simple Silverlight 3 application that does network detection
demo
Why Offline is So Hard
Is the network useful? Driver issuesVirtual PCs!Coffee shop problemMaybe you shouldn’t connect!
The One Take-Away Point
How do you know if you are online?
1. Can you connect to your server?2. Have you validated the response?
Microsoft can help by telling you when to try again
VB.NET Sample
REM function that gets called when the network changesPrivate Sub OnNetworkChange (ByVal s As Object, _ ByVal a As EventArgs)
REM Perform detection hereEnd Sub
REM set up the system to call that functionPublic Sub New() AddHandler NetworkInformation. _ NetworkChange.NetworkAddressChanged, _ AddressOf OnNetworkChangeEnd Sub
C# Sample
private void OnNetworkChange (Object sender, EventArgs Args){ // Put network detection here}
public MainPage(){ NetworkChange.NetworkAddressChanged += new NetworkAddressChangedEventHandler (OnNetworkChange);}
Patterns For Your Code
Ask the user
Before you connect, validate
Constantly validate results
Ask the User
Add two buttons to your application
One is “retry” and tries to connect again
The other is “offline mode” and prevents the application from even trying
Before You Connect, Validate
Put a standard file on your serverDownload and check contentsNo server==really offlineRevalidate on network change
Got a file from your server, but it’s not yours? You might be have the “coffee shop” problem and must retry
Constantly Check Results
Check all downloadsNot just status code!No server==really offlineRevalidate on network change
Got a file from your server, but it’s not yours? You might be have the “coffee shop” problem and must retry
The One Take-Away Point
How do you know if you are online?
1. Can you connect to your server?2. Have you validated the response?
Microsoft can help by telling you when to try again
Thank you!
Questions?
My email is [email protected]
NCL (System.Net) blog is http://blogs.msdn.com/ncl/
The team forum is http://social.msdn.microsoft.com/Forums/en-US/ncl/threads/
Please Complete an Evaluation FormYour feedback is important!
Evaluation forms can be found on each chairTemp Staff at the back of the room have additional evaluation form copies
© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after
the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
Extra Slides!
These slides go into more detail about the advantages and disadvantages of the different code patterns for network detection
Advantages of Ask the User
The user might know that they’ve done something special (but undetectable) to go on lineThe user might also know that it’s a bad time to go online
Disadvantages to Ask the User
The user might not know that they’ve gone online (and get it wrong)They also probably think it’s your job normally
Advantages of the Before Pattern
It’s simpleYou only have to understand one file (and you can just make it XML)
Disadvantages of "Before"
It’s not always possible to drop a file on your company serverIt has an extra bit of work at startupSometimes the network changes, but you don’t detect it in time (and ruin a downloaded file)
Advantages of Constantly Check
Starts up faster – no extra file to downloadRequires no changes to your server
Disadvantages to Constantly Check
Checking is hard! You have to understand all of the different file types that your application might haveChecking is “noisy”: there are lots of reasons why your server might not have given a good reply
