Windows Phone 8 - 4 Files and Storage

Oliver Scheer
Senior Technical Evangelist
Microsoft Deutschland
http://the-oliver.com
Files and Storage in
Windows Phone 8

• WP7.1IsolatedStorage and
IsolatedStorageSettings APIs
• Local Storage and Isolated Storage
• Windown Phone Runtime
Windows.Storage programming
Agenda
In This Session…
3/18/20142
• Special Folders
• Shared/Media
• Shared/ShellContent
• Shared/Transfers
• Exploring the local folder with ISET
• Using Removable SD cards

• Local Database
• No change from WP 7.1
• See
• http://channel9.msdn.com/Series/Mango-Jump-Start/Mango-Jump-Start-08a-
Application-Data-Storage-on-Windows-Phone--Part-1
• http://channel9.msdn.com/Series/Mango-Jump-Start/Mango-Jump-Start-08b-
Application-Data-Storage-on-Windows-Phone-Part-2
• SQLite database (native only)
Not Covered in this Module…
3/18/2014Microsoft confidential3

Persistent Storage in
Windows Phone 8

Local Data Storage: Overview




 Application
Settings File
App
Application
Files
Package
Manager
Installation
Folder
WP7.1: “App Data”
WP8 Storage
APIs or
WP7 Isolated
Storage APIs
Install
DB
Database file
DB Database
File (r/o)

File Type/ API
Installation
Folder
Local Folder Example
Local Database data
context
appdata:/ isostore:/
MyDataContext db = new MyDataContext
("isostore:/mydb.sdf")
Files access using
WP7.1 Isolated
Storage API
not supported
StorageFile and
StorageFolder
APIs
var isf =
IsolatedStorageFile.GetUserStoreForApplication()
File access using
Windows.Storage API
via URIs
ms-appx:///
ms-
appdata:///local/
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
var localFolder =
Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile storageFile =
await localFolder.GetFileAsync("CaptainsLog.store");
Different Methods For Addressing Storage Locations

• Three ways of getting a reference to the same file:
// WP7.1 IsolatedStorage APIs
var isf = IsolatedStorageFile.GetUserStoreForApplication();
IsolatedStorageFileStream fs = new IsolatedStorageFileStream("CaptainsLog.store", FileMode.Open, isf));
...
// WP8 Storage APIs using URI
StorageFile storageFile = await Windows.Storage.StorageFile.GetFileFromApplicationUriAsync(
new Uri("ms-appdata:///local/CaptainsLog.store "));
...
// WP8 Storage APIs
Windows.Storage.StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile storageFile = await localFolder.GetFileAsync("CaptainsLog.store");
...
WP8 File Access Alternatives

Storing Data using WP7.1
Isolated Storage APIs

Isolated Storage Classes
• The IsolatedStorage classes are all in the System.IO.IsolatedStorage namespace
• IsolatedStorageFile
• Represents an isolated storage area containing files and directories
• IsolatedFileStream
• Exposes a file stream access to a file stored within isolated storage
• IsolatedStorageSettings
• Dictionary<(Of <(TKey, TValue>)>) that stores key-value pairs
in isolated storage

Saving Data
private void saveGameToIsolatedStorage(string message)
{
using (IsolatedStorageFile isf =
IsolatedStorageFile.GetUserStoreForApplication())
{
using (IsolatedStorageFileStream rawStream = isf.CreateFile("MyFile.store"))
{
StreamWriter writer = new StreamWriter(rawStream);
writer.WriteLine(message); // save the message
writer.Close();
}
}
}

Loading Data
private string loadString()
{
string result = null;
using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication())
{
if (isf.FileExists("Myfile.store")
{
using (IsolatedStorageFileStream rawStream = isf.OpenFile(filename, System.IO.FileMode.Open))
{
StreamReader reader = new StreamReader(rawStream);
result = reader.ReadLine();
reader.Close();
}
}
}
return result;
}

Demo 1: Using
Isolated Storage

Application Settings
• If you just want to store setting information
• Username = “Fred”
• TextColor = “Green”
• ..you can use the ApplicationSettings object in Isolated Storage
• You use this as you would a dictionary
• You then write the object to persistent storage

Saving Data in Settings
• The storage works as a dictionary
• But you have to remember to call Save when you have finished adding keys
void saveString(string message, string name)
{
IsolatedStorageSettings.ApplicationSettings[name] =
message;
IsolatedStorageSettings.ApplicationSettings.Save();
}

Loading from Settings
• Test for the key before you try to find it or you will get an exception thrown
1
5
string loadString(string name)
{
if (IsolatedStorageSettings.ApplicationSettings.
Contains(name))
{
return (string)
IsolatedStorageSettings.ApplicationSettings[name];
}
else
return null;
}

Demo 2: Using
Settings Storage

Using Windows
Phone Runtime
Storage
3/18/2014

Windows.Storage Classes
• Windown Phone Runtime storage classes are in the Windows.Storage
namespace
• StorageFolder
• Represents a storage area containing files and directories
• StorageFile
• Represents a file and provides methods for manipulating them
• Not supported on Windows Phone 8:
• ApplicationData.LocalSettings
• Use custom file or IsolatedStorageSettings

Saving Data – Using StorageFolder
using System.IO;
using Windows.Storage;
…
private async void saveToLocalFolderAsync(string message)
{
// Get a reference to the Local Folder
StorageFolder localFolder = ApplicationData.Current.LocalFolder;
// Create the file in the local folder, or if it already exists, just open it
StorageFile storageFile = await localFolder.CreateFileAsync("Myfile.store",
CreationCollisionOption.OpenIfExists);
Stream writeStream = await storageFile.OpenStreamForWriteAsync();
using (StreamWriter writer = new StreamWriter(writeStream))
{
await writer.WriteAsync(logData);
}
}

Loading Data
using System.IO;
using Windows.Storage;
…
private async string loadStringAsync()
{
string theData = string.Empty;
// Get a reference to the file in the Local Folder
StorageFolder localFolder = ApplicationData.Current.LocalFolder;
StorageFile storageFile = await localFolder.GetFileAsync(“Myfile.store"));
// Open it and read the contents
Stream readStream = await storageFile.OpenStreamForReadAsync();
using (StreamReader reader = new StreamReader(readStream))
{
theData = await reader.ReadToEndAsync();
}
return theData;
}

Accessing Files Using ms-appdata:///local/ or ms-appx:///
// There's no FileExists method in WinRT, so have to try to open it and catch exception instead
StorageFile storageFile = null;
bool fileExists = false;
try
{
// Try to open file using URI
storageFile = await StorageFile.GetFileFromApplicationUriAsync(
new Uri("ms-appdata:///local/Myfile.store"));
fileExists = true;
}
catch (FileNotFoundException)
{
fileExists = false;
}
if (!fileExists)
{
await ApplicationData.Current.LocalFolder.CreateFileAsync("Myfile.store",
CreationCollisionOption.FailIfExists);
}
...

• Windows Phone 8 implementation of Windows.Storage is a subset of Windows 8 WinRT
• All data storage uses the LocalFolder (equivalent to WP7.1 IsolatedStorage)
• Not Supported:
• Roaming Data Store: ApplicationData.Current.RoamingFolder
• Temporary Data Store: ApplicationData.Current.TemporaryFolder
• Local Settings: ApplicationData.Current.LocalSettings
• Roaming Settings: ApplicationData.Current.RoamingSettings
Windows Phone 8 – Windows 8 Compatibility
Only LocalFolder Supported
3/18/201422

• In Windows 8, you can programmatically load an Image file that you have included in your
app package into a XAML <Image> element using the URI syntax, as follows:
RecipeImage.Source = new System.Windows.Media.Imaging.BitmapImage(
new Uri(@"ms-appx:///Images/french/French_1_600_C.jpg", UriKind.RelativeOrAbsolute));
• In Windows Phone 8, you cannot use the URI syntax in this way. Continue to use the
relative path to the image, as in Windows Phone OS 7.1:
RecipeImage.Source =
new System.Windows.Media.Imaging.BitmapImage("/Images/french/French_1_600_C.jpg");
Windows Phone 8 – Windows 8 Compatibility
Programmatically Accessing Image Files
3/18/201423

Local Folder
• All read-write I/O operations
restricted to local folder
• Create a files and folder structure
hierarchy
• Use Isolated Settings storage to
store application settings

Reserved Folders
• In addition to general data storage, the local folder
is used for the following special-use scenarios:
• Shared/Media - Apps can use this folder to
display album art in the Universal Volume Control
(UVC) while playing background audio
• Shared/ShellContent - Background images for
Tiles can be stored in isolated storage, but must
be located in this folder or a subfolder of it
• Shared/Transfers – Storage area used by the
Background File Transfer service
3/18/201427

Data Serialization
and Deserialization

Data Serialization
Data persistence and the app lifecycle
• App Launch
• App being dormant/tombstoned
• App being reactivated
• App being terminated
Not running
Launching
Running
Deactivated
/Closing

Why Serialize?
• Serializers write the properties of a collection of
objects into a file so they can be stored in persistent
storage
• Deserializers reverse this: read data out of a file and
use it to ‘re-hydrate’ a collection of in-memory
objects
• Many different serializers are available:
• XmlSerializer
• DataContractSerializer
• DataContractJsonSerializer
• Third party…
3/18/201430

Serialization using DataContractSerializer
public class MyDataSerializer<TheDataType>
{
public static async Task SaveObjectsAsync(TheDataType sourceData, String targetFileName)
{
StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync(
targetFileName, CreationCollisionOption.ReplaceExisting);
var outStream = await file.OpenStreamForWriteAsync();
DataContractSerializer serializer = new DataContractSerializer(typeof(TheDataType));
serializer.WriteObject(outStream, sourceData);
await outStream.FlushAsync();
outStream.Close();
}
...
}
List<MyDataObjects> myObjects = ...
await MyDataSerializer<List<MyDataObjects>>.SaveObjectsAsync(myObjects, "MySerializedObjects.xml");
• To use:

Deserialization using DataContractSerializer
public class MyDataSerializer<TheDataType>
{
public static async Task<TheDataType> RestoreObjectsAsync(string fileName)
{
StorageFile file = await ApplicationData.Current.LocalFolder.GetFileAsync(fileName);
var inStream = await file.OpenStreamForReadAsync();
// Deserialize the objects.
DataContractSerializer serializer =
new DataContractSerializer(typeof(TheDataType));
TheDataType data = (TheDataType)serializer.ReadObject(inStream);
inStream.Close();
return data;
}
...
}
List<MyDataObjects> myObjects
= await MyDataSerializer<List<MyDataObjects>>.RestoreObjectsAsync("MySerializedObjects.xml");
• To use:

Demo 4: Serialization
to Local Folder

Tools: Isolated
Storage Explorer

Isolated Storage Explorer
• Isolated Storage Explorer is a command-line tool you use to list, copy, and replace files and
directories in Isolated Storage
• Can be used on emulator or device
• Can be used for applications that target Windows Phone OS 7.0, 7.1 and 8.0
• at Program Files (x86)Microsoft SDKsWindows Phonev8.0ToolsIsolatedStorageExplorerTool
• Syntax:
ISETool.exe <ts|rs|dir[:device-folder]> <xd|de> <Product GUID> [<desktop-path>]
 ts–Takesnapshot
 rs–Restoresnapshot
 dir–Liststhefilesor
directories
 xd–targettheemulator
 de–targetdevice
 Guid–ProductIDfromthe
WPAppManifest.xmlfilefortheapp
 Desktop-path–directoryonyour
computerwhereisolatedstoragefilesare
writtentoorcopiedfrom

Isolated Storage Explorer Example

• Windows Phone 8 devices support SD cards
• App can read files stored on a storage card
• Must declare the ID_CAP_REMOVABLE_STORAGE capability in the application
manifest file
• Cannot write files - Access is Read Only
• Can only access file types for which your app has registered a file association in
WMAppManifest.xml
External Storage (SD Card)
3/18/2014

• You can only open files for which you have declared a File Association in WMAppManifest.xml
• Edit WMAppManifest.xml using the XML editor, not the Manifest editor
• Add a FileTypeAssociation element inside the Extensions element
• The Extensions element must follow immediately after the Tokens element
• Note that the ContentType attribute on the FileType element is required
<Extensions>
<FileTypeAssociation Name=“foo" TaskID="_default" NavUriFragment="fileToken=%s">
<SupportedFileTypes>
<FileType ContentType="application/foo">.foo</FileType>
</SupportedFileTypes>
</FileTypeAssociation>
</Extensions>
Declare a File Association to WMAppManifest.xml

API Description
ExternalStorageDevice Represents an SD card. Use the ExternalStorageDeviceExternalStorageID()
property to uniquely identify a card.
ExternalStorage.GetExtern
alStorageDevicesAsync()
Returns a collection of SD cards that are inserted in the phone. This
collection will contain no more than one SD card.
ExternalStorageFolder Represents a folder on the SD card. Use the ExternalStorageFolderPath()
property to access the folder later.
ExternalStorageFile Represents a file on the SD card. Use the ExternalStorageFilePath()
property to access the file later.
ExternalStorageDeviceGet
FileAsync() and
ExternalStorageDeviceGet
FolderAsync()
Obtain a file or folder directly from the external storage device object.
External Storage APIs

Quota Management
• There are no quotas on Windows Phone!
• Applications must make careful use of space
• Use only is necessary
• Be transparent about storage usage
• Manage application data
• Delete temporary data and files when no longer required
• Consider synchronizing or archiving data to the cloud to reduce device storage
42

Serialization and Threads
• If your status information is a complex object you can easily save the object by serializing
it
• Serialization may slow down the saving and loading of data
• You should consider the use of threading in this situation
• Perform your loading and saving on a separate thread so that the application stays
responsive
43

The information herein is for informational
purposes only an 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.
© 2012 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.
MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION
IN THIS PRESENTATION.

Windows Phone 8 - 4 Files and Storage

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