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Revision as of 15:40, 9 November 2012 by jinek (Talk | contribs)

Introduction and best practices for IsolatedStorageSettings

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This article shows most convenient way of using IsolatedStorageSettings.

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Article Metadata
Code Example
Source file: [File:IsolatedStorageSample.zip]
Tested with
SDK: [1]
Compatibility
Platform(s): Windows Phone 7.5 and 8.0
Windows Phone 8
Windows Phone 7.5
Article
Keywords: IsolatedStorageSettings, Isolated Storage, User Settings-->
Created: jinek (09 Nov 2012)
Last edited: jinek (09 Nov 2012)

Contents

Introduction

IsolatedStorageSettings - is dictionary-like way for permanent storing values in Isolated Storage. All you have to do to store a value is provide a key for this value and a value itself. You can store there anything you want: user settings, layout information or application state. All settings from IsolatedStorageSettings are accessible after application rerun. In this tutorial we are going create a simple application that keeps one value and then we will extend it for more convenient use.

Basic Sample

  1. Run Visual Studio 2012
  2. Create new Windows Phone project (7.5 or 8.0)
  3. Navigate to MainPage.xaml and replace all control content with one checkbox:
<phone:PhoneApplicationPage x:Class="IsolatedStorageSample.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}">
<CheckBox Content="Switch option"
Name="chck"
Checked="chck_Checked"
Unchecked="chck_Unchecked"
VerticalAlignment="Top" />
</phone:PhoneApplicationPage>
  1. Navigate to MainPage.xaml.cs and add some code here:
using System.IO.IsolatedStorage;
using System.Windows;
 
namespace IsolatedStorageSample
{
public partial class MainPage
{
/// <summary>
/// Object for sync access to IsolatedStorage
/// </summary>
private readonly object _sync = new object();
 
private const string SwitchKeyName = "switch";
 
// Constructor
public MainPage()
{
InitializeComponent();
//checking if property exists, if no - create it
if (!IsolatedStorageSettings.ApplicationSettings.Contains(SwitchKeyName))
{
IsolatedStorageSettings.ApplicationSettings[SwitchKeyName] = true;
SaveSettings();
}
 
//the checkbox state initializing
chck.IsChecked = (bool) IsolatedStorageSettings.ApplicationSettings[SwitchKeyName];
}
 
private void chck_Checked(object sender, RoutedEventArgs e)
{
IsolatedStorageSettings.ApplicationSettings[SwitchKeyName] = true;
SaveSettings();
}
 
private void chck_Unchecked(object sender, RoutedEventArgs e)
{
IsolatedStorageSettings.ApplicationSettings[SwitchKeyName] = false;
SaveSettings();
}
 
/// <summary>
/// Saving settings to isolated storage
/// </summary>
private void SaveSettings()
{
lock (_sync)
{
IsolatedStorageSettings.ApplicationSettings.Save();
}
}
}
}
  1. Run the application

IsolatedStorageSettings is easy to use. But if you are going to have more then just one setting-value - syncing, keeping key name, checking if setting exists and saving each time it been updated may become a headache. Better way is to provide all this functionality by helper class only once.

Improvement

Easier way to work with IsolatedStorageSettings is to create a wrapper class around it. It would save the settings every time we update a value (in a thread safe way), it would automatically set default value if setting does not exist (and does not throw an exception when you try to access not existen value), and finally it keeps the key name - we have to provide it only once during property declaration. Create two new classes:

using System.IO.IsolatedStorage;
 
namespace IsolatedStorageSample
{
/// <summary>
/// Helper class is needed because IsolatedStorageProperty is generic and
/// can not provide singleton model for static content
/// </summary>
internal static class IsolatedStoragePropertyHelper
{
/// <summary>
/// We must use this object to lock saving settings
/// </summary>
public static readonly object ThreadLocker = new object();
 
public static readonly IsolatedStorageSettings Store = IsolatedStorageSettings.ApplicationSettings;
}
 
/// <summary>
/// This is wrapper class for storing one setting
/// Object of this type must be single
/// </summary>
/// <typeparam name="T">Any serializable type</typeparam>
public class IsolatedStorageProperty<T>
{
private readonly object _defaultValue;
private readonly string _name;
private readonly object _syncObject = new object();
 
public IsolatedStorageProperty(string name, T defaultValue = default(T))
{
_name = name;
_defaultValue = defaultValue;
}
 
/// <summary>
/// Determines if setting exists in the storage
/// </summary>
public bool Exists
{
get { return IsolatedStoragePropertyHelper.Store.Contains(_name); }
}
 
/// <summary>
/// Use this property to access the actual setting value
/// </summary>
public T Value
{
get
{
//If property does not exist - initializing it using default value
if (!Exists)
{
//Initializing only once
lock (_syncObject)
{
if (!Exists) SetDefault();
}
}
 
return (T) IsolatedStoragePropertyHelper.Store[_name];
}
set
{
IsolatedStoragePropertyHelper.Store[_name] = value;
Save();
}
}
 
private static void Save()
{
lock (IsolatedStoragePropertyHelper.ThreadLocker)
{
IsolatedStoragePropertyHelper.Store.Save();
}
}
 
public void SetDefault()
{
Value = (T) _defaultValue;
}
}
}

This class is not hard to understand and you can extend it as you want (may be you want to save values only on application shutdown?). Using this class is easier as IsolatedStorageSettings:

namespace IsolatedStorageSample
{
using System.Windows;
 
public partial class MainPage
{
static readonly IsolatedStorageProperty<bool> SwitchProperty = new IsolatedStorageProperty<bool>("switch",true);
 
public MainPage()
{
InitializeComponent();
chck.IsChecked = SwitchProperty.Value;
}
private void chck_Checked(object sender, RoutedEventArgs e)
{
SwitchProperty.Value = true;
}
 
private void chck_Unchecked(object sender, RoutedEventArgs e)
{
SwitchProperty.Value = false;
}
}
}

We are still working only around one setting but as you can see a lot of lines are gone! Lets create another setting - FirstRunTimeProperty:

using System;
 
namespace IsolatedStorageSample
{
using System.Windows;
 
public partial class MainPage
{
static readonly IsolatedStorageProperty<bool> SwitchProperty = new IsolatedStorageProperty<bool>("switch",true);
 
/// <summary>
/// Keeps first run time
/// </summary>
static readonly IsolatedStorageProperty<DateTime> FirstRunTimeProperty = new IsolatedStorageProperty<DateTime>("firstruntime", DateTime.Now);
 
public MainPage()
{
InitializeComponent();
chck.IsChecked = SwitchProperty.Value;
Loaded+=OnLoaded;
}
 
private void OnLoaded(object sender, RoutedEventArgs routedEventArgs)
{
//MessageBox.Show - could freeze main thread for a long time
//Dont let it freeze the constructor
MessageBox.Show(FirstRunTimeProperty.Value.ToString());
//This MessageBox always shows time of first run
}
 
private void chck_Checked(object sender, RoutedEventArgs e)
{
SwitchProperty.Value = true;
}
 
private void chck_Unchecked(object sender, RoutedEventArgs e)
{
SwitchProperty.Value = false;
}
}
}

FirstRunTimeProperty lets me know when was first application run.

You can run the application two or more times to test it.

Good practice is to create a special static class, that would contain all your settings in it, so you can access any property in a program in any time you want, like this:

namespace IsolatedStorageSample
{
public static class SettingsContainer
{
public static readonly IsolatedStorageProperty<bool> TestProperty1
= new IsolatedStorageProperty<bool>("TestProperty1");
public static readonly IsolatedStorageProperty<string> TestProperty2
= new IsolatedStorageProperty<string>("TestProperty2", "This is a test property");
//...
}
}

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