The way I ended up solving this was as follows. Remember I need to extract the localized texts from a database/remote api.
With this solution I can databind like this and all bound texts will change automatically when I change the language:
<Label Content="{Binding Path=Strings.ErrorLevelColumnHeaderLabel}"/>
Of course the Strings object must be accessible from all datacontexts.
The strings are stored in a database table that looks like this, an ID-column and one column for each of the supported languages:
ID en da de 24 'Level' 'Niveau' 'Stufe'
I created a UIStringsVM class which implements the INotifyPropertyChanged interface. In my example I have implemented this in a base class called Observable, which I am sure many others have as well. See this answer for details.
public class UIStringsVM : Observable { public static UIStringsVM CurrentStringsInstance; private bool stringsAreLoading = false; private Dictionary<int, string> stringDictionary; }
The UIStringsVM class have a property for each string I need to have localized. Since the class supports the INotifyPropertyChanged interface through the base class I can then rely on changes to be reflected in the UI when ever the language changes.
Inside the UIStringsVM class the strings for the current language is stored in a Dictionary<int, string>. The reason for this is that I can use the string ID from the database to access the correct string.
Now I can use the ID inside the property Get method to return whatever string is stored for that value. So the properties will look like this:
public string ErrorLevelColumnHeaderLabel { get => this.stringDictionary[24].Replace("\\n", Environment.NewLine); private set => this.stringDictionary[24] = value; }
The properties are never set individually so the setter could be omitted.
The constructor:
public UIStringsVM() { this.stringDictionary = new Dictionary<int, string>(); // Initialize with default values. The ! at the end makes it easier to identify missing values in the database. this.LoginButtonText = "Login!"; this.LogoutButtonText = "Logout!"; this.UserLabelFormatString = "{0} logged in!"; this.ErrorLevelColumnHeaderLabel = "Level!"; UIStringsVM.CurrentStringsInstance = this; }
In order to load the strings I use the following method:
public async Task LoadStringsAsync(string languageCode, CancellationToken ct) { if (languageCode.Length != 2) throw new ArgumentException("languageCode must be exactly 2 characters.", nameof(languageCode)); this.StringsAreLoading = true; var client = new UIStringsClient(AppVM.BaseURL); try { var apiStrings = await client.GetByLanguageAsync(languageCode, ct); foreach (var r in apiStrings) { /* Note: this will make it impossible to overwrite a string with an empty string from the database, * thus always keeping the string defined in this class' constructor. However strings will always * have a value as defined in the constructor even if one does not exist in the database. * */ if (string.IsNullOrWhiteSpace(r.Value)) continue; this.stringDictionary[r.Key] = r.Value; } this.OnPropertyChanged((string)null); // Raise a change event for the entire object, not just a named property } finally { this.StringsAreLoading = false; } }
I hope this helps anyone who might happen to come across this late answer. I have been running this solution for 15 months or so, and its been really great to work with.
