Introduction

Developing websites to support multiple languages can be a challenging and time-consuming process. With standard HTML pages this involves creating and maintaining duplicate versions of each page for each supported language as well as having the language content embedded into the HTML, where content cant easily be edited. While the process improved slightly with the introduction of scripting technologies such as ASP and PHP, no significant development or maintenance time was saved. For those of you who have to develop multi-lingual interfaces and applications, youll be glad to know that ASP.Net makes things considerably easier.

ASP.Net and the .Net framework ship with support for multilingual applications, namely in the form of Resource Files, the CultureInfo class and the System.Globalization and System.Resources.ResourceManager namespaces. Unfortunately in its present state, localizing content in ASP.Net applications is still a tedious process. Like everything else .Net though, the object model and sheer power available makes extending what's already available and developing new functionality to support better localization easy as 1 - 2 - 3.

Before we get started

Basics

The way localization works in .Net is fairly straightforward. Content is stored in a pretty simple XML files called Resource Files. You create a Resource File for each supported language (more can be added later on). When the application is compiled, the resource files are embedded into assemblies - the default resource file is embedded in the main assembly (.dll file), language-specific resource files are embedded into their own assemblies called satellite assemblies. Resource files are pretty simple and look a lot like a Hashtable, they have a name and a value - the name is the same for all resource files, and the value is a language specific translation of some content. In essence, this allows you to use the System.Resources.ResourceManager class to do things like:

UserNameLabel.Text = myResourceManager.GetString("Username");
UserNameValidator.ErrorMessage = myResourceManager.GetString("RequiredUsername");

The resource manager will automatically load the right resource file based on the current thread's CurrentCulture value - more on this in the next section. Hopefully you are already seeing a lot of potential. Some of the key highlights are:

• Content is separated into simple XML files
• There's a separate XML file for each supported language
• The code to load values is relatively simple and short
• The ResourceManager class automatically retrieves the content from the right XML file based on the thread's CurrentCulture value
• You can easily have 1 actual page, for N supported language

Cultures

It's important to have a good understanding of Cultures since our new code will make use of them - specifically the System.Globalization.CultureInfo class and the culture name value which follows the RFC 1766 naming standard. Basically, you create a new CultureInfo instance by specifying the culture name in the constructor:

CultureInfo c = new CultureInfo("en-US"); //creates a CultureInfo instance for American English
CultureInfo c = new CultureInfo("en-AU"); //creates a CultureInfo instance for Australian English
Cultureinfo c = new CultureInfo("he-IL"); //creates a CultureInfo instance for Israel Hebrew

Once you have a CultureInfo instance, you can set the current thread's UIculture to it, which will make your ResourceManager in the above code automatically fetch the content from the right XML resource file.

CultureInfo c = new CultureInfo("en-US"); //creates a CultureInfo instance for American English
System.Threading.Thread.CurrentThread.CurrentCulture = c; //Will automatically format dates and such
System.Threading.Thread.CurrentThread.CurrentUICulture = c; //Used by the ResourceManager to get the correct XML File

Download dummy application

Why not use what's available as-is?

• Resource files are embedded into [satellite] assemblies
• Resource files can't return strongly-typed objects
• Web controls aren't easily hooked with resource files

Building a better Resource Manager

1. The public method GetString which is used throughout the application to access the required resource
2. The private method GetResource which gets a Hashtable either from the cache or by calling LoadResource
3. The private method LoadResource which parses the XML file and stores it into the cache

GetString()

public static string GetString( string key) {
 Hashtable messages = GetResource();
        if (messages[key] == null){
  messages[key] = string.Empty;
#if DEBUG
  throw new ApplicationException("Resource value not found for key: " + key);
#endif
 }
 return (string)messages[key];
}

The method accepts a single argument, the key of the resource we want to get. It then retrieves a Hashtable of content using GetResource, which is culture-aware and returns us the correct Hashtable. If the requested key doesnt exist, well throw an exception if the application is in DEBUG mode, else well simply return an empty string.

GetResource()

private static Hashtable GetResource() {
 string currentCulture = CurrentCultureName;
 string defaultCulture = LocalizationConfiguration.GetConfig().DefaultCultureName;
 string cacheKey = "Localization:" + defaultCulture + ':' + currentCulture;
  if (HttpRuntime.Cache[cacheKey] == null){
   Hashtable resource = new Hashtable();
   LoadResource(resource, defaultCulture, cacheKey);
  if (defaultCulture != currentCulture){
   try{
    LoadResource(resource, currentCulture, cacheKey);
   } catch (FileNotFoundException){}
  }
 }
 return (Hashtable)HttpRuntime.Cache[cacheKey];
}

The GetResource() method is slightly more complicated. Its goal is to retrieve a Hashtable which can be looked up by a key to retrieve a value. The method will first look to see if the Hashtable has already been loaded and cached [line: 5]. If so, it simply returns the value from the cache. Otherwise it will use LoadResource() to parse the appropriate XML file [lines: 6-13]. Something worthy of noting is that the "appropriate XML file" is actually a mix of the XML file for the current culture as well as the one for the default culture. The default culture is specified in the configuration file [line: 3], and the current culture is retrieved from the current thread's current culture [line: 2].

First the default culture is loaded [line: 8], and then the current culture is loaded [line: 11]. This means if a key is defined in both XML files (which most should be), the default value will be overridden by the culture-specific value. But if it doesnt exist in the culture-specific value, the default value will be used.

LoadResource()

private static void LoadResource(Hashtable resource, string culture, string cacheKey) {
 string file = LocalizationConfiguration.GetConfig().LanguageFilePath + '\\' + culture + "\\Resource.xml";         
 XmlDocument xml = new XmlDocument();
 xml.Load(file);
  foreach (XmlNode n in xml.SelectSingleNode("Resource")) {
    if (n.NodeType != XmlNodeType.Comment){
      resource[n.Attributes["name"].Value] = n.InnerText;
   }
  }
  HttpRuntime.Cache.Insert(cacheKey, resource, new CacheDependency(file), DateTime.MaxValue, TimeSpan.Zero);
}

LoadResource loads the XML file [line: 4] (it gets the root path from our configuration file [line: 2]) and simply parses it while loading the values into our hashtable [line: 5 - 9]. Finally, the hashtable is stored in the Cache [line: 10].

Other enhancements

Wrappers

There are a number of minor enhancements which can be done to our ResourceManager class. For example, I build bilingual webpages in English and French. Annoyingly, in English a colon is always glued to the word it follows, but in French there has to be a space. For example:

Username:  //English
Nom d'utilisateur : //French

This means the colon needs to be localized. Instead of using the GetString() method, we can simply build a wraper:

public static string Colon {
 get { return GetString("colon"); }
}

In our English resource file the colon would simply be ':', while in the French one it would have a space ' :'.

Strongly-typed resources

The reason we use Hashtable instead of a NameValueCollection is because the ResourceManager class can be expanded to return strongly-typed objects. For example, you might have localized help content which is more than just a single value. It might have a title, an example and the help text. While exploring this is beyond the scope of this article (perhaps a part 3??) the capability exists.

Localized Controls

Our next goal is to make our life easier when developing a website by expanding existing server controls (literals, labels, buttons) to be localization-aware. We begin by creating a very simple interface our new controls will implement.

ILocalized

public interface ILocalized{
 string Key {get; set; }
 bool Colon {get; set; }
}

ILocalized defines a Key property which will be passed to our ResourceManager's GetString() method. In order to show how you can expand these classes to fit your own needs, I've also included a Colon property as a boolean, which will tell our controls if they shoudl append a colon at the end of their value.

LocalizedLiteral

public class LocalizedLiteral : Literal, ILocalized {
        #region fields and properties
        private string key;
        private bool colon = false;
   
        public bool Colon {
           get { return colon; }
           set { colon = value; }
        }
   
        public string Key {
           get { return key; }
           set { key = value; }
        }
        #endregion
   
   
        protected override void Render(HtmlTextWriter writer) {
           base.Text = ResourceManager.GetString(key);
           if (colon){
              base.Text += ResourceManager.Colon;
           }
           base.Render(writer);
        }
}

Rinse, wash and repeater

public class Localized Button  : Button, ILocalized {
   
        #region Fields and Properties
        private string key;
        private bool colon = false;
   
        public string Key {
           get { return key; }
           set { key = value; }
        }
   
        public bool Colon {
           get { return colon; }
           set { colon = value; }
        }
   
        #endregion
   
        protected override void Render(HtmlTextWriter writer) {
           base.Text = ResourceManager.GetString(key);
           if (colon){
              base.Text += ResourceManager.Colon;
           }
           base.Render(writer);
        }
}

using System.Web.UI;
using System.Web.UI.WebControls;
   
  namespace Localization {
     public class LocalizedLinkButton : LinkButton, ILocalized {
        #region Fields and Properties
        private string key;
        private bool colon;
        private string confirmKey;
   
        public string ConfirmKey {
           get { return confirmKey; }
           set { confirmKey = value; }
        }
        public string Key {
           get { return key; }
           set { key = value; }
        }
         public bool Colon {
           get { return colon; }
           set { colon = value; }
        }
        #endregion
   
        protected override void Render(HtmlTextWriter writer) {
           if(key != null){
              Text = ResourceManager.GetString(key);
              if (colon) {
                 Text += ResourceManager.Colon;
              }
           }
           if (confirmKey != null) {
              Attributes.Add("onClick", "return confirm('" + 
                        ResourceManager.GetString(confirmKey).Replace("'", 
                        "\'") + "');");
           }
   
           base.Render(writer);
        }
   
     }
}

Using Localized Controls

You use the localized controls like any other server control. First register the control on the page:

<%@ Register TagPrefix="Localized" Namespace="Localization" Assembly="Localization" %>

Then, without having to write and code, you can simply add the control either by drag and dropping it in the designer, or in the HTML mode by typing:

<Localized:LocalizedLiteral id="passwordLabel" 
 runat="server" Key="password" Colon="True" />
<Localized:LocalizedButton id="login"
 runat="server" colon="false" Key="login" />

Download

The best thing to do now is to play a bit with some code. I've again created a sample site (similar to the previous one), but this time using our new ResourceManager class and Localized controls. You might need to change the web.config's languageFilePath property to point to the right folder.