Monthly Archives: September 2017

Globalization and localization in ASP.NET Core – Part 3

If you just landed on this page, this page is of series of Post for localization / globalization

Part 1 – Introduction

Part 2 – ASP.NET Core ways of Localization / Globalization

Part 3 – Old trustworthy ResourseManager

If you are following the series of post, in this post, I would talk about working with ResourceManager.

ResourceManager class is nothing new, It been there since the inception of .NET framework. It was the de facto mechanism for working with localize resource file before aspnet core introduce IStringLocalizer.

In this post, I want to demonstrate, ResourceManager still works in dotnet core, if you don’t want to go with fuzzy IStringLocalizer.

Let dive in to the code, in the sample application, you fill find two methods in HelloController. In Local method

 string rsFileName = "api1.Resources.rs1";
 ResourceManager rm = 
       new ResourceManager(rsFileName, Assembly.GetExecutingAssembly());
 string msg = rm.GetString("Hello");

Here, it creating new instance of the ResourceManager which take basename and assembly where these resource files are embedded.

Basename is the root name of the resource file without its extension but including any fully qualified namespace name. For example, the root name for the resource file named
MyApplication.MyResource.en-US.resources is MyApplication.MyResource.

Assembly needs to be the one where resource files are embedded. In our case it is same as the one where running code (HelloController) is present. I can get current assembly which contains the code by Assembly.GetExecutingAssembly() which returns api1.dll assembly

In our case, resources file which ResourceManager will read are name rs1.resx and placed in “Resources” folder. Hence, basename will be api1.Resources.rs1

ResourceManager.GetString will looks for current culture on running thread and respectively look for culture specific resource file to get the value of key “Hello”


If culture specific resource is not found, say “de-de“, it will use default resource with any suffix for getting the value of the “key“. If “key” values isn’t found in the resource file, it will return value as “key” itself.

If you need to get resource value for any other culture than the current culture on the running tread, you can by specifying the culture in the GetString method.

string msg3 = rm.GetString("Hello", new System.Globalization.CultureInfo("fr-FR"));

As simple as that.

Now, level 2. I had requirement where code for reading resource was in another assembly/dll then the one where resource files are located.

If you look into the lib method, it calls Lib1.ResRdr library to get the resource file message. But, rs1.resx is in api1.dll, not in Lib1.Rdr.dll

 public string lib()
   string msg = "";
   msg = Lib1.ResRdr.Messenger.GetHello(); 
   return msg;

If you look into GetHello() method

public static string GetHello()
   string msg = "";
   Assembly asm = Assembly.GetCallingAssembly();
   string rsFileName = asm.GetName().Name + ".Resources.rs1";
   ResourceManager rm = new ResourceManager(rsFileName, asm);
   var msg2 = rm.GetString("Hello");
   msg = msg2;
   return msg;

It creates new ResourceName, pass the basename and assembly which contains the embedded resource. Since, it seperate dll, it get’s the calling assembly by Assembly.GetCallingAssembly() which would return api1.dll or api2.dll, whichever calls  Lib1.Rdr.dll. Note, here if you had use Assembly.GetExecutingAssembly(), you will get Lib1.Rdr.dll.

For the basename, since resources are embedded in the dll, assembly root namespace needs to be taken from the assembly name. i.e. api1, api2. So, basename would be api1.Resources.rs1 or api2.Resources.rs2

Rest would be taken care by the ResourceManager, it would read remote assembly embedded resources and it’s satellite assemblies to get the translated value.

That’s all for Globalization and localization in ASP.NET Core. Hope you find this series of post informative.


Globalization and localization in ASP.NET Core – Part 2

If you just landed on this page, this page is of series of Post for localization / globalization

Part 1 – Introduction

Part 2 – ASP.NET Core ways of Localization / Globalization

Part 3 – Old trustworthy ResourseManager

In this post, I would be hinting on the ASP.NET Core way of  Localization / Globalization. There is already a good post on this from the Microsoft official Docs for ASP.NET Core at and I am not going to repeat what’s in that post but would be sharing few highlight’s of that article.

In order to work with IStringLocalizer, important, you need to add following in the Startup.cs

// Add Localization services to the system
services.AddLocalization(options => options.ResourcesPath = "Resources")

// Configure supported cultures and localization options
services.Configure<RequestLocalizationOptions>(options =>
       var supportedCultures = new[]
                              new CultureInfo("en-US"),
                              new CultureInfo("de-DE")

// State what the default culture for your application is. 
// This will be used if no specific culture can be determined for 
// a given request.

options.DefaultRequestCulture = new RequestCulture("en-US", "en-US");

// You must explicitly state which cultures your application supports.
// These are the cultures the app supports for formatting 
// numbers, dates, etc.

options.SupportedCultures = supportedCultures;

// These are the cultures the app supports for UI strings, 
// i.e. we have localized resources for.

options.SupportedUICultures = supportedCultures;

In Configure in Startup.cs:

// Configure localization.
var locOptions = app.ApplicationServices.GetService<IOptions<RequestLocalizationOptions>>();

This code (UseRequestLocalization) would set current culture info and current ui culture on the request execution thread.

By default, It determines culture from QueryString, Cookie and Request Header. Read first post to get some insight.

In order to understand better, I have create a sample application and have put the it on the GitHub, where you can get the execution in action.

In HelloController.cs, local method on api1, you could see this code

string cul = Thread.CurrentThread.CurrentCulture.Name;
string culUI = Thread.CurrentThread.CurrentUICulture.Name;

If you debug this application, if your startup.cs initialization code is correct, it would see the set the thread culture.

In the same method, it set the localize string from IStringLocalizer _localizer.

msg = _localizer["Hello"];

This _localizer in injected in the controller by ASP.NET Core dependency injection, and would read from HelloController resources


Placement and name of this resources file are important, otherwise, it won’t be able to read it. Great extent of naming and placement is written at That’s all you need to work with IStringLocalizer.

If you are curious just as me, to find out how this IStringLocalizer works? Then, you need to checkout it official GitHub Repository,

Dotnet Core is opensource, and you can read it code. When Dependency Inject (DI) is called to inject IStringLocalizer, it calls the ResourceManagerStringLocalizerFactory, which in turn create an instance of ResourceManagerStringLocalizer.

When ResourceManagerStringLocalizerFactory creates the instance of ResourceManagerStringLocalizer, it add new instance of the ResourceMananger

protected virtual ResourceManagerStringLocalizer 
                                                 Assembly assembly,
                                                 string baseName)
    return new ResourceManagerStringLocalizer(
                        new ResourceManager(baseName, assembly),

ResourceManager then in turn work with the resource files to get the translated text for the key

msg = _localizer["Hello"];

Here, “Hello” is the key and whatever value in the resource file, it will get that. Resource + culture file to be specific.

IStringLocalizer –> DI –> ResourceManagerStringLocalizerFactory –> ResourceManagerStringLocalizer –> ResourceManger

That’s the flow, how IStringLocalizer translated the messages.

Few interesting points here,

Type and Resource File Naming

IStringLocalizer takes the type. i.e.

IStringLocalizer<HelloController> _localizer

HelloController is the type. You resource needs to have HelloController name without default language resource file. What does in mean?

In ResourceManager era, default language resource file which won’t have culture suffix, example, abc resource would be named

"abc.FR-fr.resx" //French
"abc.ES-es.resx" //Spanish

“abc.resx” is default, if for any other cultures is pass apart from “FR-fr”, “ES-es”, this file would be used.

But, when working with IStringLocalizer, your default language set in Startup.cs. (see startup.cs code at top) Hence, you resource file should be named



Location of resource files

In the startup.cs code, you mention resource path, where to find all the resources. It doesn’t need to “Resources”, it could be anything. When assembly is build, resource file would go as emended resources into the dll. ASP.NET Core would build satellite assemblies for different culture which you have mention.


By definition, satellite assemblies do not contain code, except for that which is auto generated. Therefore, they cannot be executed as they are not in the main assembly. However, note that satellite assemblies are associated with a main assembly that usually contains default neutral resources (for example, en-US). A big benefit is that you can add support for a new culture or replace/update satellite assemblies without recompiling or replacing the application’s main assembly.

Dotnet Peek view of assembly


ResourceManager would find the resources embedded in assembly / satellite assembly base on the resource path and type name.



It all good, when you are going translation in the same assembly, where resource files are located. But, in my case, resource file where in one assembly, and code to read from resource file was in another assembly. This where ASP.NET Core IStringLocalizer faded and was limited to for me. I need to resorted to good old ResourceManager which I would describe in the other post.








Globalization and localization in ASP.NET Core – Part 1

Here, this post is about my experience in the globalization and localization in core application.

This is series of Post for localization / globalization

Part 1 – Introduction

Part 2 – ASP.NET Core ways of Localization / Globalization

Part 3 – Old trustworthy ResourseManager

First for the fresher folks, let me explain what’s globalization and localization

Say, you need an web application which caters to different language say English and French. Greeting like “Hello Friend” needs to be translated to “salut l’ami” in french. How do we do it, simple. Create file with Name Value, on for English and other for French.

TextTranslate-English.txt -> Greeting =  “Hello Friend”

TextTranslate-English.txt -> Greeting =  “salut l’ami”

In Code -> var message  = TextTranslate[“Greeting”]

Base on the language, it will pick from the respective file. This is the idea of Globalization and localization. Dotnet folks figure this out long before in .NET 1.1 framework and in same can be done with Resource files in .NET.

In Visual Studio, you can add resource file to your project.

This resource file contain the key and value. Say, here Key is “Hello” and Value is “Hello-en-us”

Similarly, you can add different culture resource file.

In dotnet, language has more than text, it’s how you write dates, format numbers, currency symbols, etc. So, they call collection of this as culture

e.g. US English = 12/25/2017, UK English = 25/12/2017

Culture are denote by two letter alphabets like en, or en-US, en-UK. That’s US English and UK English. es-ES is Spanish Spain and es-MX Spanish Mexico. If just es is mention, then it defaults to Spanish Spain, en defaults to en-US.

And the class which handle this is known as cultureinfo. The thread in runs your code has two properties CultureInfo and UICultureInfo

Culture is the .NET representation of the default user locale of the system. This controls default number and date formatting and the like.

UICulture refers to the default user interface language, a setting introduced in Windows 2000. This is primarily regarding the UI localization/translation part of your app.

You can get running thread Culture with following code

 CultureInfo cul = Thread.CurrentThread.CurrentCulture;
 CultureInfo culUI = Thread.CurrentThread.CurrentUICulture;

Now, In ASP.NET, say your server in running in UK and you got the request from France. How does ASP.NET application know, it have to serve french text?

Fortunately, in ASP.NET Core, there is middleware which does it for us. By default, it has three ways

  • QueryString
  • Cookie
  • AcceptLanguage Header




You can read Cookie as

The cookie format is c=%LANGCODE%|uic=%LANGCODE%, where c is Culture and uic is UICulture, for example: c=en-UK|uic=en-US


You can write cookie with following code

 new CookieOptions { Expires = DateTimeOffset.UtcNow.AddYears(1) });


When browser makes the request to website, it will send accept-language header. As seen in Chrome debug window -> Network -> Request Headers


You can read more about it here,

This middleware would set the thread.currentCulture and thread.currentUICulture using either QueryString, Cookie or Accept-Language Header

Once current culture is set, Date.ToString() will return date as per Current culture. In en-US it would be 12/25/2017 and en-UK, it would be 25/12/2017

Next post we will see, how to implement localization package and how to use it.