How to localize your webapp with Asp Net Core and DewLocalizationMiddleware

I’ve started to use Asp Net .core some month ago, and I like it. However, some approach used by default from the system like configuration options or localization for me are a little “old style”.

In this case, lets take the localization like example. Here how it works.


The middleware has the DewLocalizationMiddlewareOptions type. If you don’t want customize anything you can just call the middleware with his Usexxx method. However you can customize a bit the middleware with the options.

Here the type with default values.



By default the middleware assume the language “en-us”. Every language file must by a “<lang>.json” where <lang> is a choosed string from the cookie or the default language.

In default case the file is called “en-us.json”, obviously you can change the default value.

For example you can leave “en-us” like default value, and call the other files “fr-fr”,”it-it”,”it-ch”, etc. and use this notation in the cookie.

NOTE : default language works only when the call to the first file (for example “it-it”) fails.


By default the middleware assume that the localization folder is in the main project folder and it’s called “Localization”.

You can change it, however be carefull that you don’t need to place the “/” at the end of the new Path string.

For example if you want place it into a directory called “Language/Dictionaries/it-it.json” Path must be “Language/Dictionaries”.


This is just the language Cookie name. Call it how you want. Default value is “lang”.

CustomNameWORKS ONLY IN > V. 2.1.0

If you need a custom name for HttpContext item you can set it here, just remember to pass to GetDewLocalizationTranslator (HttpContext extension class method).

Default is “DewLocalization”

How add middleware to pipeline

NOTE : If no file are present, ever the default file, the middleware throw an exception.

Remember to add the:

to use the UseDewLocalizationMiddleware method

Use Translator like a service

If you don’t want use the localization middleware as middleware in the pipeline, you can use it like a service. This is how you can do it.

In this case, you should use the dependency injection to get the translator:

you can see in the next example how to work with it in both ways.

NOTE: if you set the translator as a service you cannot read the dictionary from HttpContext, and same is the inverse (if you use it like middleware it will not work with D-Injection)

NOTE: You can set both way (but why?)

Work with Translator

Middleware expose an Helper class, the DewTranslator.

If you want use it, you need to remember to add this into using section:

After that, in the controller.

Differences between service and middleware

The main difference is that in the middleware way the dictionary will be read automatically in a point of request pipeline, and you after this can use it just calling HttpContext.GetDewLocalizationTranslator().

In the service way, you just inject the object with its options to controller, but before you can use it, you need to read the dictionary by calling method GetDictionaryFromFiles(HttpContext)

After that, the use is the same.


Source code


You can find it on nuget with the name DewLocalizationMiddleware