1. Data Storage, Backup and Roaming
11/15/2018
Windows XAML
Building Apps for Windows Phone 8.1 Jump Start
Data Storage, Backup and Roaming
Matthias Shapiro @matthiasshap
Andy Wigley @andy_wigley
29 April 2014
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

2. This module… (50 minutes)
Data Storage and Data Roaming
Local Settings
Roaming files and settings
The Windows Storage API
Serializing objects using the XML and Json serializers
Using Compression
Using the SD Card to store application data
Known Folders

3. App Data Locations

4. Locations where apps can access data
11/15/2018
Locations where apps can access data
Networks
Credential Locker
File Picker APIs
File System
B/ground Transfer
r/w
Temp
App data Folders
r/w
r/w
Roaming
App data Folders
Local
Pictures Videos Music
- Direct access needs manifest capabilities
App data Folders
App
Known Folders
r/w
r/w
Installation Folder
SD Card
r/o
r/w
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

5. App Data Storage: Overview
Installation Folder
Package Manager installs all app files into the Installation Folder
Read-only access from app
Read-only reference database
Apps store data in Local Folder
Settings and properties in the app dictionary
Unstructured data in Isolated Storage files
Structured data in database files
Package Manager
Creates root folder
sandboxed to App
Install DB
Files (r/o)
App Data Folder
App
Creates/Manages
files and settings
WinRT Storage APIs DB
Local or Roaming
Settings File
Application
Files
Database file

6. Data Storage Areas Windows.Storage.ApplicationData
11/15/2018
Data Storage Areas
Windows.Storage.ApplicationData
Windows.Security. Credentials
Roaming
Folder
Settings
Other devices can access what you put in here
Data roamed cross-device
Limited to 100kb per application
Held in OneDrive storage
Local
Folder
Settings
Store local data here for use by your application
Can store data up to the limit of the storage on the device
Retained if the application is updated
Temp
Folder
Use for temporary storage
No guarantee it will still be here next time your program runs
Cleaned up in a low storage condition
PasswordVault
Credentials
Credential Locker
Use for secure storage of PasswordCredential objects
Data roamed cross-device
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

7. Windows.Storage.ApplicationData
11/15/2018
Windows.Storage.ApplicationData
This namespace provides access to the three storage folders in the app data store and the application settings containers:
Windows.Storage.StorageFolder roam = Windows.Storage.ApplicationData.Current.RoamingFolder;
Windows.Storage.StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFolder temp = Windows.Storage.ApplicationData.Current.TemporaryFolder;
Windows.Storage.ApplicationDataContainer localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
Windows.Storage.ApplicationDataContainer roamingSettings = Windows.Storage.ApplicationData.Current.RoamingSettings;
The StorageFolder object represents a folder and is used to access the folder and its contents
The ApplicationDataContainer object represents a key-value pair settings dictionary
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

8. Local and Roaming Settings

9. Local Settings // Create a simple setting
11/15/2018
Local Settings
// Create a simple setting
localSettings.Values["exampleSetting"] = "Hello Windows";
// Read data from a simple setting
Object value = localSettings.Values["exampleSetting"];
if (value == null) {
// No data }
else
// Access data in value
// Delete a simple setting
localSettings.Values.Remove("exampleSetting");
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

10. Roaming Settings and the Roaming Folder
11/15/2018
Roaming Settings and the Roaming Folder
If a user obtains your application and installs it on multiple devices it is nice if all the devices can share the same settings information
Changes on one device are reflected on all the other devices owned by that user
Roaming data is shared between Windows Phone 8.1 Store Apps and Windows 8.1 Store Apps that have the same Package Family Name (PFN)
Roaming data provides a way that an application can synchronise data and/or settings across a number of different physical devices
It takes the form of a folder and a settings dictionary which are automatically stored in the users’ OneDrive
Roaming data is limited to value of ApplicationData.RoamingStorageQuota (usually 100KB) but do not count against the users’ OneDrive quote
If your roaming data exceeds the quota, it won’t roam until its size is less than the quota again
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

11. 11/15/2018
Roaming Data
Other clients are notified of updated data via Windows Notification Service. If app is running when sync occurs, an event is raised.
Sync engine transfers data periodically based on triggers (user idle, battery, network, etc.)
PFN 12345
Roaming
folder
Roaming
settings
OneDrive stores up to 100kb of roaming data per app (not included in user quota). If app exceeds the limit, sync stops.
WP 8.1 App – PFN 12345
Roaming
Local
Temp
Windows App – PFN 12345
Roaming
Local
Temp
App writes data using standard file/settings APIs.
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

12. Using the Roaming settings
private void name_TextChanged(object sender, TextChangedEventArgs e) {
Windows.Storage.ApplicationDataContainer roamingSettings =
Windows.Storage.ApplicationData.Current.RoamingSettings;
roamingSettings.Values["userName"] = name.Text; }
The RoamingSettings are exposed as a dictionary into which an application can save data
The data is persisted on the device and also shared with other devices
Note: On Windows 8.1, there is a special HighPriority setting. This has no effect on Windows Phone.

13. Reading the Roaming settings
Windows.Storage.ApplicationDataContainer roamingSettings =
Windows.Storage.ApplicationData.Current.RoamingSettings;
if (roamingSettings.Values.ContainsKey("userName")) {
name.Text = roamingSettings.Values["userName"].ToString(); }
This code queries the roaming settings by using the key name
The name will be reflected across multiple devices (including Windows 8.1 ones)

14. Receiving notification when roaming data changes
The DataChanged event fires when the roaming data has changed
Windows.Storage.ApplicationData.Current.DataChanged += Current_DataChanged;
...
void Current_DataChanged(ApplicationData sender, object args) {
// Refresh your settings... }
The event is only fired if the application is active at the time of the change
You should still load up all your data when your app starts

15. Tips on using roaming data
Applications can store data in the roaming folder as they would any other folder on the device, or in roaming settings in the same way as local settings
The synchronisation takes place in the background
Good for app customisation settings, most recent activity, partially completed work
Bad for synchronising large amounts of data or “instant syncing” scenarios
Last writer wins
HighPriority setting is available on Windows for quick sync, but has no effect on Windows Phone

16. Debugging apps using the Roaming Folder
Developers can install an application on multiple unlocked devices
You can debug the roaming folder with a device connect to your PC
Locking a developer device will trigger the synchronisation
If you have problems:
Make sure that files are closed correctly
Make sure that the devices are running the same version of the application

17. Roaming Settings demo 11/15/2018
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

18. File Access

19. Different Methods For Addressing Storage Locations
File Type/ API
Installation Folder
App data folder
Example
File access using Windows.Storage API via URIs
ms-appx:///
ms-appdata:///local/ ms-appdata:///roaming/ ms-appdata:///temp/
var file = await Windows.StorageFile.GetFileFromApplicationUriAsync( new Uri("ms-appdata:///local/AppConfigSettings.xml"));
File access using Windows.Storage API via StorageFolder references
Windows. ApplicationModel.Package.Current. InstalledLocation
Windows.Storage. ApplicationData. Current .LocalFolder / .RoamingFolder / .TempFolder
var localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile storageFile = await localFolder.GetFileAsync("CaptainsLog.store");

20. Writing a complete file
11/15/2018
Writing a complete file
This method will create a file from a string of text
All the file operations are asynchronous
private async void writeTextToLocalStorageFile(string filename, string text) {
StorageFolder fold = Windows.Storage.ApplicationData.Current.LocalFolder;
StorageFile file =
await fold.CreateFileAsync(filename, CreationCollisionOption.ReplaceExisting);
await FileIO.WriteTextAsync(file, text); }
Sets the target folder
Sets action if file already exists
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

21. Reading a complete file
This method will read a file into a string
private async Task<string> readTextFromLocalStorage(string filename) {
var fold = Windows.Storage.ApplicationData.Current.LocalFolder;
StorageFile file = await fold.GetFileAsync(filename);
string result = await FileIO.ReadTextAsync(file);
return result; }

22. Writing a Complete File
11/15/2018
Writing a Complete File
demo
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

23. 11/15/2018
Using Streams
As well as writing a complete file in one action using the FileIO API, you can also create a stream and write to this
The read and write operations are asynchronous
Streams handle the difference in latency between one type of storage (e.g. memory) and another (e.g. network or file system)
Streams are used all over WinRT
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

24. Writing to a file using a Stream
private async void WriteToStreamButton_Click(object sender, RoutedEventArgs e) {
StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
StorageFile file = await localFolder.CreateFileAsync("JumpStart.txt");
string userContent = InputTextBox.Text;
if (!String.IsNullOrEmpty(userContent))
using (StorageStreamTransaction transaction = await file.OpenTransactedWriteAsync())
using (DataWriter dataWriter = new DataWriter(transaction.Stream))
dataWriter.WriteString(userContent);
transaction.Stream.Size = await dataWriter.StoreAsync(); // reset stream size to override the file
await transaction.CommitAsync(); }

25. 11/15/2018
Using a Stream
demo
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

26. Using XML and JSON serilializers

27. Storing Objects
We have seen that it is easy to read and write settings and blocks of text
However it is also useful to be able to store objects
The serialization libraries in Windows Phone make it very easy to persist structured data using serialisation
An application can serialise data into XML or JSON formats
The data will be stored or transferred as text

28. Serialization Rules
XML Serializer requires that the object must have a parameterless constructor
Private and static members of the class will not be persisted
Be careful of app upgrades: If you add members to the class in an app update and restore from a data file that was created by serializing using the previous class definition, you will have problems

29. Using a Serializer This code serializes a collection of customers
using (Stream stream = await notesFolder.OpenStreamForWriteAsync(filename,
CreationCollisionOption.OpenIfExists)) {
DataContractJsonSerializer serializer =
new DataContractJsonSerializer(typeof(Customer[]));
serializer.WriteObject(stream, customers); }
This code serializes a collection of customers

30. Using a Serializer This creates the serializer
using (Stream stream = await notesFolder.OpenStreamForWriteAsync(filename,
CreationCollisionOption.OpenIfExists)) {
DataContractJsonSerializer serializer =
new DataContractJsonSerializer(typeof(Customers));
serializer.WriteObject(stream, customers); }
This creates the serializer
The constructor is given the type of the object to store

31. Using a Serializer
using (Stream stream = await notesFolder.OpenStreamForWriteAsync(filename,
CreationCollisionOption.OpenIfExists)) {
DataContractJsonSerializer serializer =
new DataContractJsonSerializer(typeof(Customers));
serializer.WriteObject(stream, customers); }
This writes the collection of customers to the output stream

32. Deserializing the data
using (Stream stream = await notesFolder.OpenStreamForReadAsync(filename)) {
DataContractJsonSerializer serializer =
new DataContractJsonSerializer(typeof(Customers));
Customers result = serializer.ReadObject(stream) as Customers; }
The read process is the reverse of the writing one
Note that we have to cast the result of ReadObject(Stream) to the required type

33. XML Serialization This is how you save to an XML format file
This is how you load from an XML format file
XmlSerializer serializer = new XmlSerializer(typeof(Customers));
serializer.Serialize(stream, customers);
XmlSerializer serializer = new XmlSerializer(typeof(Customers));
Customers result = serializer.Deserialize(stream) as Customers;

34. Compression

35. Using Windows.Storage.Compression.Compressor
11/15/2018
Using Windows.Storage.Compression.Compressor
var s = await destFile.OpenAsync(FileAccessMode.ReadWrite);
Compressor compressor =
new Compressor(s.GetOutputStreamAt(0), CompressAlgorithm.Mszip, 0);
An application can use compression when it saves and loads data
The compression stream can be used as any other stream, but it compresses the data as it is transferred
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

36. Compression Algorithms
var s = await destFile.OpenAsync(FileAccessMode.ReadWrite);
Compressor compressor =
new Compressor(s.GetOutputStreamAt(0), CompressAlgorithm.Mszip, 0);
There are a number of different algorithms available:
Lzms
Mszip
Xpress
XpressHuff
You can also set the block size for the compression, the value 0 means use the default

37. Using Decompressor
var s = await destFile.OpenAsync(FileAccessMode.ReadWrite);
Compressor compressor =
new Compressor(s.GetOutputStreamAt(0), CompressAlgorithm.Mszip, 0);
The Decompressor complements the Compressor and provides an input stream that can be used to decompress files

38. Credential Locker securely store and roam user credentials

39. Overview APIs to store credentials (user name, password) securely
Windows.Security.Credentials
Benefits:
Secure storage
Credential isolation
Roaming

40. Isolation Apps can only access their own credentials App A App B
Locker
App Sandbox Boundary
App B

41. Roaming MSA Credentials roam across trusted devices App App 11/15/2018
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

42. Credential Locker sample
void SaveCredential(string username, string password) {
PasswordVault vault = new PasswordVault();
PasswordCredential cred = new PasswordCredential("MyAppResource", username, password);
vault.Add(cred); }
IReadOnlyList<PasswordCredential> RetrieveCredential(string resource)
return vault.FindAllByResource(resource);

43. Credential Locker
demo

44. Known Folders

45. KnownFolders
KnownFolders is an API which simplifies the view the developer has of accessible user data on the phone
Rather than searching through all the possible different locations on the device for a particular type of file a program can request a single list of all the files
This includes files on the SD card (if inserted) along with files held on the device
Files in KnownFolders are visible to all apps (that have registered the proper capabilities)
Consider using the FileOpenPicker API as an alternative to allow users to select a file in these folders
No capabilities required as consent is implied
Covered in Session 10

46. KnownFolders Physical View Logical View Internal storage
11/15/2018
KnownFolders
Physical View
Logical View
Internal storage
KnownFolders.PicturesLibrary.GetFilesAsync()
C:\Users\Public\Pictures\Seattle\
StorageFile: Pic01.jpg
C:\Users\Public\Pictures\Birthday\
StorageFile: Pic01.jpg
C:\Users\Public\Pictures\Pic01.jpg
StorageFile: Pic02.jpg
SD Card (if present)
D:\Pictures\Portland\
D:\Pictures\Birthday\
D:\Pictures\Pic01.jpg
D:\Pictures\Pic02.jpg
D:\Pictures\Hawaii\Pic02.jpg
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

47. Accessing User Content
11/15/2018
Accessing User Content
var pictures = await Windows.Storage.KnownFolders.PicturesLibrary.GetFilesAsync();
KnownFolders provides access to:
Pictures
Videos
Music
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

48. Accessing Known Folders
11/15/2018
Accessing Known Folders
demo
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.

49. Using the SD Card

50. The SD Card in Windows Phone 8.1
Phone applications now have read/write access to the SD Card
Apps can store their own files and also make use of files already on the card
This makes it possible for applications to share data amongst themselves
There is full SD Card support provided by the emulator
Maps to a local folder on your PC
Because SD cards represent a “shared” resource, the application must declare file associations in the manifest for each file type it wants to access

51. Setting SD card capabilities
Before an app can use the SD card you need to set some capabilities
Removable Storage
If you are using KnownFolders API, you may also need:
Pictures Library
Videos Library
Music Library
If these capabilities are not set the program will throw an exception when it runs

52. Applications and file associations
A given application is not able to work with just any type of file stored on the SD card
An application must declare associations with the file types that it works with
An image processing program will work with files such as .jpg, .png, etc
A sound processing program will work with .mp3 files
You can add your own custom file types for your particular application if you wish
The associations are set in the manifest
Note that this is not required for applications accessing files in their own local/roaming/temporary storage
This is the same mechanism used for app-to-app communications through file associations (See Session 10)

53. Setting file associations for your application
The manifest for your application must specify the file types that are associated with it
It will only be able to open files with that type
This application can only work with .txt files

54. Getting an SD Card
var devices = Windows.Storage.KnownFolders.RemovableDevices;
var sdCards = await devices.GetFoldersAsync();
if (sdCards.Count == 0) return;
StorageFolder firstCard = sdCards[0];
These statements get a reference to the SD card on the phone
They are part of a method that creates a file on the SD card
This method is part of the demo software we will be running later

55. Getting an SD Card
var devices = Windows.Storage.KnownFolders.RemovableDevices;
var sdCards = await devices.GetFoldersAsync();
if (sdCards.Count == 0) return;
StorageFolder firstCard = sdCards[0];
We get a list of SD cards using the KnownFolders API
There will only be 0 or 1

56. Getting an SD Card
var devices = Windows.Storage.KnownFolders.RemovableDevices;
var sdCards = await devices.GetFoldersAsync();
if (sdCards.Count == 0) return;
StorageFolder firstCard = sdCards[0];
If there is not one present the value of the Count property will be 0
This method returns if there are no SD Cards on the device
Your application must handle this eventuality gracefully
Not all devices have an SD card slot
The slot might not have a card fitted into it

57. Getting an SD Card
var devices = Windows.Storage.KnownFolders.RemovableDevices;
var sdCards = await devices.GetFoldersAsync();
if (sdCards.Count == 0) return;
StorageFolder firstCard = sdCards[0];
The card is exposed as a StorageFolder, so we can use it in the same way the previous devices we have seen
We can create folders and files
But we can only work with files types for which we have declared a file association in the manifest

58. Inserting an SD card in the emulator
The emulator provides support for SD cards
You just map it to the folder that you are going to use
When you press the Insert SD Card the emulator behaves exactly as if a card has been inserted into the phone

59. SD Cards in the Emulator
The emulator will create the Documents, Music, Pictures and Videos folders in your SD card folder if they are not already present
It can also use media from the folder
This is a great way to get your content in the emulator for testing

60. Ejecting an SD Card from the emulator
You can also eject an SD card
Writes to the card may be synchronised when the card is ejected
There is an option to select this
We will use the SD card in the next section

61. Reading and Writing Json using the SD card storage
11/15/2018
Reading and Writing Json using the SD card storage
demo
© 2013 Microsoft Corporation. All rights reserved. Microsoft, Windows, 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.