Windows 10 UWP: How to Read and Save Settings Easily

In the UWP Application model, reading and saving settings are very similar to WinRT API. The class we are using is ApplicationData.Current.LocalSettings It is using key-value-pair to store settings.

LocalSettings will stay on the user's current computer, and not being synced with thier Microsoft account.

The API to save settings is:

LocalSettings.Values[key] = value;

To read settings: 

if (LocalSettings.Values.ContainsKey(key))
{
    return LocalSettings.Values[key];
}

Please notice, we should first check if the key is already present.

In order to use it in an easy way, we can write a class to manage those settings:

public class AppSettings : INotifyPropertyChanged
{
    public bool ShowTimeSheetSetting
    {
        get
        {
            return ReadSettings(nameof(ShowTimeSheetSetting), true);
        }
        set
        {
            SaveSettings(nameof(ShowTimeSheetSetting), value);
            NotifyPropertyChanged();
        }
    }

    public ApplicationDataContainer LocalSettings { get; set; }

    public AppSettings()
    {
        LocalSettings = ApplicationData.Current.LocalSettings;
    }

    private void SaveSettings(string key, object value)
    {
        LocalSettings.Values[key] = value;
    }

    private T ReadSettings<T>(string key, T defaultValue)
    {
        if (LocalSettings.Values.ContainsKey(key))
        {
            return (T)LocalSettings.Values[key];
        }
        if (null != defaultValue)
        {
            return defaultValue;
        }
        return default(T);
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void NotifyPropertyChanged([CallerMemberName]string propName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
    }
}

Key Points:

1. By taking advantage of C#6, the key is a type of string, we can use nameof to retrieve it's name. When we invoke event handlers, we can also use ?. for null check.

2. Using generics to do the type convertion. If the property got a default value, return it. Because in our App, default values are ususally needed. In this example, I only added one settings of a bool type: ShowTimeSheetSetting

3. The operation that the AppSettings class is exposing is just the getter and setter on the property. Reading and Saving settings are automatically done internally. The user of this class don't have to know about how this is done, which means, if some day, the implementation for how to read and save settings changes, we just need to modify one place not everywhere in the code. 

4. Because we implemented INotifyPropertyChanged we can do two way bindings on XAML:

<Page.Resources>
    <core:AppSettings x:Key="AppSettings" />
</Page.Resources>

<ToggleSwitch OnContent="On" OffContent="Off" IsOn="{Binding Source={StaticResource AppSettings}, Path=ShowTimeSheetSetting, Mode=TwoWay}" />

For other types of settings, such as string, int, enum, we can of course added them as properties, and use them in xaml just like this!