May 27, 2014
Loren Horsager
CEO, Founder

LOREN HORSAGER
 20 years of software consulting
 Created about
50 mobile apps
 Founder of
Mobile
Composer

LOCAL STORAGE - USE CASES
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LOCAL STORAGE
 Key/Value pairs
 Files
 Text Files
 Binary Data
 Serialized Files
 Database (SQLite)

KEY/VALUE PAIRS
 Simple Data
 User Settings
 Personalization info
 Login tokens
 Supports syncing to iCloud

KEY/VALUE PAIR DEMO

SIMPLE STORAGE
 Download from Component Store (free)
 using PerpetualEngine.Storage;
 Consistent across platforms (Android, iOS,
Win)
 Registry like data storage

SIMPLE STORAGE DEMO

KEY/VALUE PAIRS
 Not secure
 Saved with App Updates
 Stored in Library/Preferences

FILE STORAGE
Writeable Long term Saved on
Updates
.app/
Documents
Library
Library/Preferences
Library/Caches tmp
X
X
X
(Use
NSDefaults)
X
X
X
X
X
X
X
X
X
X
Saved to iCloud by
Default
Visible to User in iTunes
X
X
X
X

SYSTEM.IO
 Standard .NET library
 File, Directory, FileInfo, Path

PATHS
Path
.app/ ./
Documents var documents = Environment.GetFolderPath (Environment.SpecialFolder.MyDocuments);
Library var library = Path.Combine (documents, "..", "Library");
Library/Preferences Use NSDefaults var cache = Path.Combine (documents, "..", "Library", "Caches"); Library/Caches tmp var tmp = Path.Combine (documents, "..", "tmp");

SHARING FILES VIA ITUNES
 Documents directory will automatically be shared
 To Disable:
 Change UIFileSharingEnabled in Info.plist
 Users can only see root directory
 Users can change files in Documents directory so make sure it doesn’t impact your app

ICLOUD BACKUP
 Limit the amount of data going to iCloud
 Users get 5GB for all apps
 Limit to files that can’t be recreated
 To turn off iCloud syncing
 SetSkipBackupAttribute
NSFileManager.SetSkipBackupAttribute (filename, true);

APP UPDATES
 When updating app versions the contents of the following will remain
 Documents
 Library
 This includes sub folders except
Library/Caches

FILE IO DEMO

SERIALIZATION
 XML or JSON
 Great for developing frontend prior to building web services
 Great for preferences

XML SERIALIZATION DEMO

SQLITE
 When you need
 Structured data
 Complex queries
 Sorting
 Aggregating
 Efficient data storage
 Offline mode
 Shared data models

SQLITE
 Open Source
 Lightweight
 Cross Platform
 Android
 iOS
 Win
 Single file storage
 Most of SQL92 standard

SQLITE DRAWBACKS
 Some OUTER JOINS not supported
 Can’t change scheme
 Exceptions: Table rename, AddColumn
 Views are Read-only

SQLITE OPTIONS
 ADO.NET
 SQLite.NET ORM

THREADING
 Can’t share data access across threads
 Wrap all reads and writes into the same lock
} object locker = new object (); // class level private field
// rest of class code lock (locker){
// Do your query or insert here

SQLITE ADO DEMO

 ExecuteNonQuery
 ExecuteReader
 ExecuteScalar
QUERIES

SQLITE.NET ORM
 Use existing entities
 Does not support entity relationships
 Different annotations than Entity Framework
Data Annotations
 Simplifies data access

SQLITE.NET ORM DEMO

SQLITE.NET ORM ATTRIBUTES
 [PrimaryKey]
 [AutoIncrement]
 [Column(name)]
 [Table(name)]
 [MaxLength(value)]
 [Ignore]
 [Unique]

 Insert
 Get<T>
 Table<T>
 Delete
 Query<T>
 Execute
QUERIES

SQLITE SECURITY
 SQLite is file based and not encrypted
 For secure storage use SQLCipher
 Available on Xamarin Component Store

CONSIDERATIONS
 Security
 Don’t store logins directly
 Put data where it can’t be directly viewed or altered by user
 Secure SQLite
 SQLCipher – encrypted SQLite database files ($499 from
Component Store)
 iCloud
 Don’t sync more than is needed

RESOURCES
 Xamarin site
 http://docs.xamarin.com/guides/ios/application_fundamentals/working_wit h_the_file_system/
 http://docs.xamarin.com/guides/crossplatform/application_fundamentals/data/part_4_using_adonet /
 http://docs.xamarin.com/guides/crossplatform/application_fundamentals/data/part_3_using_sqlite_orm /
 SimpleStorage
 https://components.xamarin.com/gettingstarted/simple -storage/true

CONTACT
 GitHub project https://github.com/lhorsager/XamarinLocalStorage
 Presentation http://lorenhorsager.com/2014/05/27/xamarin -local-storagepresentation/
Loren Horsager
Loren.horsager@mcomposer.com
@lorenhorsager