Pawel Ciucias: LocalSettings

There are multiple ways to store user data in winRT apps, one option for simple data is the LocalSettings, now the local settings can be simply used as a key value Collection, but that's rather boring, this is because you could in essence use a Resource dictionary for the same thing.

What's interesting about the LocalSettings date Container is that it can contain sub containers, so for example you could have multiple containers in the LocalSettings container that all have the same sub valuekey pairs, what i mean is you could have something like the following

PersonOne

FirstName
LastName
BirthDate

PersonTwo

FirstName
LastName
BirthDate

PersonThree

FirstName
LastName
BirthDate

ok lets look at an example

pretty straight forward app, now let's look at the xaml to make this happen

<Page

x:Class="pc.LocalSettings.MainPage"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

xmlns:local="using:pc.LocalSettings"

xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

mc:Ignorable="d">

<Page.Resources>

</Style>

</Style>

</Style>

</Style>

</Page.Resources>

<Grid.RowDefinitions>

</Grid.RowDefinitions>

<Grid.ColumnDefinitions>

</Grid.ColumnDefinitions>

<TextBlock Grid.Column="1" Text="LocalSettings Example"

Style="{ThemeResource HeaderTextBlockStyle}"

VerticalAlignment="Center"/>

</StackPanel>

</Grid>

</Page>

easy enough, i don't think anything warrants an explanation. so let's just jump into the code-behind

using System;

using System.Collections.Generic;

using Windows.Storage;

using Windows.UI.Xaml;

using Windows.UI.Xaml.Controls;

namespace pc.LocalSettings

{

public sealed partial class MainPage : Page

{

public MainPage()

{

this.InitializeComponent();

//Get the local settings

var localSettings = ApplicationData.Current.LocalSettings;

//use the key of each of the containers as an item

//in our people combo box

foreach (var fullName in localSettings.Containers.Keys)

this.People_CB.Items.Add(fullName);

//add our event revievers

this.People_CB.SelectionChanged += People_CB_SelectionChanged;

this.Save_BTN.Click += Save_BTN_Click;

this.Delete_BTN.Click += Delete_BTN_Click;

}

//delete a contianer from our local settings

void Delete_BTN_Click(object sender, RoutedEventArgs e)

{

//get the key name from the combo box

var selectedPerson = People_CB.SelectedValue.ToString();

//get our local settings container

var localSettings = ApplicationData.Current.LocalSettings;

//delete the container with the specified key

localSettings.DeleteContainer(selectedPerson);

//remove the corresponding key from the combo box

People_CB.Items.Remove(selectedPerson);

//clear the input values

this.FirstName_TXT.Text = this.LastName_TXT.Text = String.Empty;

this.BirthDate_DP.Date = DateTimeOffset.Now;

}

//load the data for a specific container

void People_CB_SelectionChanged(object sender, SelectionChangedEventArgs e)

{

//prevent error when deleting a container

if (e.AddedItems.Count == 0)

return;

//get contaier key to load

var selectedPerson = e.AddedItems[0].ToString();

//get local settings

var localSettings = ApplicationData.Current.LocalSettings;

//load sub container with specified key

ApplicationDataContainer Person = localSettings.Containers[selectedPerson];

//populate inputs with specified container values

this.FirstName_TXT.Text = Person.Values["firstName"].ToString();

this.LastName_TXT.Text = Person.Values["lastName"].ToString();

this.BirthDate_DP.Date = (DateTimeOffset)Person.Values["birthDate"];

}

void Save_BTN_Click(object sender, RoutedEventArgs e)

{

//get values from input fields

var firstName = FirstName_TXT.Text;

var lastName = LastName_TXT.Text;

var birthDate = BirthDate_DP.Date;

//set key to use

var fullName = String.Format("{0} {1}", firstName, lastName);

//get local settings

var localSettings = ApplicationData.Current.LocalSettings;

//get or create the specified subcontaier

ApplicationDataContainer Person =

localSettings.CreateContainer(firstName, ApplicationDataCreateDisposition.Always);

//save or update the subcontainers values

SaveContainerData(Person, "firstName", firstName);

SaveContainerData(Person, "lastName", lastName);

SaveContainerData(Person, "birthDate", birthDate);

if (!this.People_CB.Items.Contains(firstName))

this.People_CB.Items.Add(firstName);

}

void SaveContainerData<T>(ApplicationDataContainer Container, string Key, T Value) {

//check if contaier already has key, if so update it if not create it.

if (Container.Values.ContainsKey(Key))

Container.Values[Key] = Value;

else

Container.Values.Add(new KeyValuePair<string, object>(Key, Value));

}

the code-behind is pretty straight forward as well, the only thing really worth mentioning, is when creating a sub container that is

ApplicationDataContainer Person = localSettings.CreateContainer(firstName, ApplicationDataCreateDisposition.Always);

you have two options
Always:loads the container if it exists or creates it if it doesn't
Existing:only loads contains that exist throws and exception if you try to create a new one.

Thursday 22 January 2015

LocalSettings