Local DatabaseFiles & Storage

Nguyen Tuan | Microsoft Certified Trainer

Agenda

• Local Data Storage: Overview

• Using Isolated Storage

• Using Setting Storage

• File & Protocol Association

• Data serialization

• Local database

• SQLite database

• External Storage(Using SD Card)

Local Data Storage: Overview

ApplicationSettings File

App

ApplicationFiles

Package Manager

Install Folder

Install

DB

Database file

DB DatabaseFile (r/o)

Installation folder

• Is a read-only folder

• Contains files of your app package

• APIs to access the installation folder:• Application.GetResourceStream(Uri) method

• DataContext class

• Package.InstalledLocation property

• StorageFile and StorageFolder classes

Local folder

• Is the root folder of your app’s data store

• Is not altered or updated when you update your app

• Will be removed when the application is uninstalled

• It may be something like this:

C:\Data\Users\DefApps\AppData\{5D93133B-3B39-4ABF-8D61-277D77B9F2AD}\Local

Application.GetResourceStream(Uri)

// Get the image stream at the specified URI that// is relative to the application package root.Uri uri = new Uri(relativeUriString, UriKind.Relative); StreamResourceInfo sri = Application.GetResourceStream(uri);

// Convert the stream to an Image object.BitmapImage bi = new BitmapImage(); bi.SetSource(sri.Stream); Image img = new Image(); img.Source = bi;

• Use this method to stream files from the installation folder

DataContext class

• To connect to a reference database that is part of the app package

• is an object representing the database, a proxy, containing Table objects that represent the tables in the database

Package.InstalledLocation property

• Returns the installation folder as a StorageFolder object

• The Path property to get the full path of the installation folder

Windows.ApplicationModel.Package package = Windows.ApplicationModel.Package.Current;Windows.Storage.StorageFolder installedLocation = package.InstalledLocation;

String output = String.Format("Installed Location: {0}", installedLocation.Path);

Windows.Storage classes

• StorateFolder• Represent a store area containing files and folders

• StorageFile• Represent a file and provide method for manipulating

Saving Data

private async void WriteMessage(String message) {StorageFolder folder = ApplicationData.Current.LocalFolder;

StorageFile file = await folder.CreateFileAsync("message.dat", CreationCollisionOption.OpenIfExists);

Stream stream = await file.OpenStreamForWriteAsync();

using (StreamWriter writer = new StreamWriter(stream)){

await writer.WriteAsync(message);}

}

Loading Data

private async Task<string> ReadMessageAsync() {string data = string.Empty;StorageFolder folder = ApplicationData.Current.LocalFolder;StorageFile file = await folder.GetFileAsync("message.dat");

Stream stream = await file.OpenStreamForReadAsync();using (StreamReader reader = new StreamReader(stream)){

data = await reader.ReadToEndAsync();}return data;

}

Isolated Storage Classes

• Isolated Storage is used to store local data

• All I/O operations are restricted to isolated storage

• IsolatedStorageFile• Represents an isolated storage area containing files and folders

• IsolatedFileStream• Exposes a file stream access to a file stored within isolated storage

• IsolatedStorageSetting• Dictionary that stores key-value pairs in isolated storage

Saving Data

private void WriteMessageToIsolatedStorage(string message) {using (IsolatedStorageFile store = IsolatedStorageFile.GetUserStoreForApplication()) {

using(IsolatedStorageFileStream stream = new IsolatedStorageFileStream("message.dat", FileMode.Append, FileAccess.Write, store)){

StreamWriter writer = new StreamWriter(stream);writer.WriteLine(message);writer.Close();

}}

}

Loading Data

private string ReadMessageFromIsolatedStorage() {string data = string.Empty;using (IsolatedStorageFile store = IsolatedStorageFile.GetUserStoreForApplication()) {

using (IsolatedStorageFileStream stream = new IsolatedStorageFileStream("message.dat", FileMode.Open, store)) {

StreamReader reader = new StreamReader(stream);data = reader.ReadToEnd();reader.Close();

}}return data;

}

Saving Data in Settings

• Is used to store app’s setting in form of key-value.

• It works like a dictionary

private void SaveSetting(string key, string value) {IsolatedStorageSettings.ApplicationSettings[key] = value;IsolatedStorageSettings.ApplicationSettings.Save();

}

private string LoadSetting(string key) {if (IsolatedStorageSettings.ApplicationSettings.Contains(key)) {

return (string)IsolatedStorageSettings.ApplicationSettings[key];}return null;

}

Special-use folders in the local folder

• Shared

• Shared/Media

• Shared/ShellContent

• Shared/Transfers

• PlatformData

File & Protocol Association

• File association allows app to launch when the user want to open a particular file type, via:• an email attachment

• a website via Internet Explorer

• a text message

• a NFC tag

• another app from the Store

WMAppManifiest.xml

Demo: FilesStorage

Serialization/Deserialization

• Convert an object into a stream of bytes in order to store the object or transmit it to memory, a database, or a file

• Binary serialization

• XML serialization

• SOAP serialization

XMLSerializer (1)

• Used to serialize/deserialize bettween objects and xml data

using System.Xml.Serialization;

[XmlRoot(“contact")]public class Contact{

[XmlElement("id")]public int ID{get;set;}[XmlElement("name")]public string Name { get; set; }[XmlElement("email")]public string Email { get; set; }

}

XMLSerializer (2) - Serialize

using System.Xml.Serialization;.. .. .. .. ..

private async void SaveContactAsync(Contact contact){StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync("contact.xml",

CreationCollisionOption.ReplaceExisting);var outStream = await file.OpenStreamForWriteAsync();XmlSerializer serializer = new XmlSerializer(typeof(Contact));serializer.Serialize(outStream, contact);await outStream.FlushAsync();outStream.Close();

}

XMLSerialize (3) – XML File

<?xml version="1.0" encoding="utf-8" ?><contact><id>1</id><name>Maria Rose</name><email>rose@live.com</email>

</contact>

Contact contact = new Contact() { ID = 1,Name = "Maria Rose",Email = "rose@live.com"

};saveContact(contact);

XMLSerializer (4) - Deserialize

using System.Xml.Serialization;.. .. .. .. ..

private async Task<Contact> LoadContactAsync() {StorageFile file = await ApplicationData.Current.LocalFolder.GetFileAsync("contact.xml");var inStream = await file.OpenStreamForReadAsync();XmlSerializer serializer = new XmlSerializer(typeof(Contact));Contact contact = (Contact)serializer.Deserialize(inStream);inStream.Close();return contact;

}

Other Serializers

• DataContractSerializer

• DataContractJsonSerializer

• Third party

Demo: XML Serializer1.DataStorage

Local database

• App can store relational data in local database

• Resides on app’s Local folder

• Use LINQ to SQL for all database operations

• LINQ provides object-relational mapping capabilites

DataContext

• DataContext is a proxy, represents the database

• Contains Table objects which represent tables on database

• Table objects is made up of entities that correspond to rows of data in a database

public class TodoDataContext:DataContext{

public static string DBConnectionString = "Data Source=isostore:/todo.sdf";

public TodoDataContext(string connectionString):base(connectionString){

}public Table<TodoItem> TodoItems;

}

Entity Class

public class TodoItem:INotifyPropertyChanged, INotifyPropertyChanging{

private int _id;[Column(IsPrimaryKey=true, IsDbGenerated=true, DbType="INT NOT NULL IDENTITY", CanBeNull=false,

AutoSync=AutoSync.OnInsert)]public int Id {

get {return this._id;

}set {

if (_id != value) {NotifyPropertyChanging("Id");this._id = value;NotifyPropertyChanged("Id");

}}

}….

}

Creating database

using (TodoDataContext db = new TodoDataContext(TodoDataContext.DBConnectionString)){

if (!db.DatabaseExists()){

db.CreateDatabase();}

}

Database operation

TodoItem newItem = new TodoItem() { Name = txtItemName.Text };items.Add(newItem);db.TodoItems.InsertOnSubmit(newItem);db.SubmitChanges();

ObservableCollection<TodoItem> items = new ObservableCollection<TodoItem>();var todoItems = from i in db.TodoItems select i;foreach (var i in todoItems) {

items.Add(i);}

Demo: Local Database

SQLite

• Is a SQL database engine

• Is self-contained

• Is serverless

• Is zero-configuration

• Is transactional

Why SQLite?

Worlds’ most popular database

Rich Features

Reliable

SQLite.org

Documentation

SQL Syntax

C/C++ API Reference

Source and tools download

SQLite for Windows Phone

• SQLite database engine is fully supported on WP8 platform

• SQLite engine for Windows Phone available as a Visual Studio extension

Csharp-sqlite

• Is an independent reimplementation of the SQLite software library

sqlite-net-wp8

• A C++/CX wrapper for SQLite functions that sqlite-net depends on.

• Can be used as an alternative to csharp-sqlite on Windows Phone 8

.NET APIs

SQLite-NETLINQ syntaxLightweight ORMSimilar to WP8 Local Database (LINQ to SQL)

SQLitePCLSQL statements

Thin wrapper around the SQLite C API

using (var db = new SQLitePCL.Database("demo.db")){

db.Open(); using (var stmt = db.PrepareStatement

("SELECT name, age FROM people")) { while (stmt.Step()) { var name = stmt.GetTextAt(0); var age = stmt.GetIntAt(1);

}}

}

var db =new SQLite.SQLiteAsyncConnection(App.DBPath);

var _customer = await(from c in db.Table<Customer>() where c.Id == customerIdselect c).FirstOrDefaultAsync();

if (customer != null) {

var Id = _customer.Id; var Name = _customer.Name;

}

Installing SQLitePCL to your Solution

1. Add Reference to SQLite extension SDK2. In Configuration Manager, change

target platform to X86 or ARM3. In ‘Manage NuGet Packages’, add

reference to SQLitePCL package

Defining tables

SQLitePCL is really a thin wrapper around the SQLite ‘C’ APIInteract with the database using

SQL statementsParameterized queries and statements

Create database and tables

private void LoadDatabase()

{

// Get a reference to the SQLite database

conn = new SQLiteConnection("sqlitepcldemo.db");

string sql = @"CREATE TABLE IF NOT EXISTS

Customer (Id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,

Name VARCHAR( 140 ),

City VARCHAR( 140 ),

Contact VARCHAR( 140 )

);";

using (var statement = conn.Prepare(sql))

{

statement.Step();

}

}

Insert

// SqlConnection was opened in App.xaml.cs and exposed through property conn

var db = App.conn;

try

{

using (var custstmt = db.Prepare("INSERT INTO Customer (Name, City, Contact) VALUES (?, ?, ?)"))

{

custstmt.Bind(1, customerName);

custstmt.Bind(2, customerCity);

custstmt.Bind(3, customerContact);

custstmt.Step();

}

}

catch (Exception ex)

{

// TODO: Handle error

}

Selectpublic Customer GetCustomer(int customerId)

{

Customer customer = null;

using (var statement = dbconn.Prepare("SELECT Id, Name, City, Contact FROM Customer WHERE Id = ?"))

{

statement.Bind(1, customerId);

if (SQLiteResult.DONE == statement.Step())

{

customer = new Customer()

{

Id = (long)statement[0],

Name = (string)statement[1],

City = (string)statement[2],

Contact = (string)statement[3]

};

}

}

return customer;

}

Update

// See if the customer already exists

var existingCustomer = GetCustomer(customer.Id);

if (existingCustomer != null)

{

using (var custstmt = dbconn.Prepare("UPDATE Customer SET Name = ?, City = ?, Contact = ? WHERE Id=?"))

{

// NOTE when using anonymous parameters the first has an index of 1, not 0.

custstmt.Bind(1, customer.Name);

custstmt.Bind(2, customer.City);

custstmt.Bind(3, customer.Contact);

custstmt.Bind(4, customer.Id);

custstmt.Step();

}

}

Delete

public void DeleteCustomer(int customerId)

{

using (var statement = dbconn.Prepare("DELETE FROM Customer WHERE Id = ?"))

{

statement.Bind(1, customerId);

statement.Step();

}

}

Demo: SQLite

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The SD Card in Windows Phone

This makes it possible for applications to share data amongst themselves

Maps to a local folder on your PC

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Setting SD card capabilities

Removable Storage

Pictures Library

Videos Library

Music Library

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Applications and file associations

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

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)

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Setting file associations for your application

This application can only work with .txt files

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Getting an SD Card

• 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

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var devices = Windows.Storage.KnownFolders.RemovableDevices;var sdCards = await devices.GetFoldersAsync();if (sdCards.Count == 0) return;StorageFolder firstCard = sdCards[0];

Getting an SD Card

• We get a list of SD cards using the KnownFolders API

• There will only be 0 or 1

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var devices = Windows.Storage.KnownFolders.RemovableDevices;var sdCards = await devices.GetFoldersAsync();if (sdCards.Count == 0) return;StorageFolder firstCard = sdCards[0];

Getting an SD Card

• 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

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var devices = Windows.Storage.KnownFolders.RemovableDevices;var sdCards = await devices.GetFoldersAsync();if (sdCards.Count == 0) return;StorageFolder firstCard = sdCards[0];

Getting an SD Card

• 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

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var devices = Windows.Storage.KnownFolders.RemovableDevices;var sdCards = await devices.GetFoldersAsync();if (sdCards.Count == 0) return;StorageFolder firstCard = sdCards[0];

Inserting an SD card in the emulator

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SD Cards in the Emulator

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Ejecting an SD Card from the emulator

There is an option to select this

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