ASP.Net core multilingual validation messages for forms

Question

I am a webform guy who wants to move to ASP.Net Core & Blazor I don't have any background in MVC just in case someone may give their feedback based on MVC.

I am interested in ASP.Net Core Razor page only.

In web form I use two files for a multilingual website, for example, I can keep related validation messages in .aspx page or in related js files if necessary, while in Core it does things differently. In webform I can keep validation message in .aspx file itself while in ASP.Net core I have been using Single Model class and Validation message is defined there.

Webform structure

-en
--index
--aboutus
..
..
-ar
--index
--aboutus

ASP.Net Core folder structure

Pages
-en
--index
--aboutus
..
..
-ar
--index
--aboutus

Let us say under Pages folder I create two folders one for English & another for Arabic and in Core we let us say I have defined my validation in Model file. Since I have one model file for both languages how can I show language specific validation message

Below code is just for example

using System;
using System.ComponentModel.DataAnnotations;

public class Starship
{
    [Required]
    [StringLength(16,
        ErrorMessage = "Identifier too long (16 character limit).")]
    public string Identifier { get; set; }

    public string Description { get; set; }

    [Required]
    public string Classification { get; set; }

    [Range(1, 100000,
        ErrorMessage = "Accommodation invalid (1-100000).")]
    public int MaximumAccommodation { get; set; }

    [Required]
    [Range(typeof(bool), "true", "true",
        ErrorMessage = "This form disallows unapproved ships.")]
    public bool IsValidatedDesign { get; set; }

    [Required]
    public DateTime ProductionDate { get; set; }
}

Problem i am facing since i have one Model file which have validation in English how can i show Validation in Arabic in most easy & simple way in ASP.Net core

Assuming my URL is like

www.example.com/en/ 
www.example.com/en/aboutus/ 
www.example.com/en/contact/

www.example.com/ar/ 
www.example.com/ar/aboutus/ 
www.example.com/ar/contact/

Can language based validation message shows just based on above URL without using any globalization feature for website pages which has any forms etc..

Answer 1

Can language based validation message be show just based on above url without using any globalization feature for website pages which has any forms etc..

Yes validation messages can be shown with reference to the culture parameter in the route. But in order for the localization to work properly you need to do some setup.

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc()
        .AddDataAnnotationsLocalization(options => {
            options.DataAnnotationLocalizerProvider = (type, factory) =>
                factory.Create(typeof(SharedResource));
        });
}

www.example.com/ar/contact/

Looking at the url, you need route data request culture provider. By default Asp.Net Core uses QueryString, Cookie and AccpetLanguageHeader culture providers (see the docs for more details), so if you want to use route value for localization you need to setup route data culture provider:

services.Configure<RequestLocalizationOptions>(ops =>
{
    ops.DefaultRequestCulture = new RequestCulture("en");
    ops.SupportedCultures = mySupportedCultures;
    ops.SupportedUICultures = mySupportedUICultures;

    // add RouteDataRequestCultureProvider to the beginning of the providers list. 
    ops.RequestCultureProviders.Insert(0, new RouteDataRequestCultureProvider(cultures));
});

But thats not all! There is many other topics to consider for properly localizing Asp.Net Core web apps :

• Views localization
• DataAnnotations localization
• ModelBinding errors localization
• IdentityDescriber errors localization
• Custom backend messages localization
• Client side validation messages localization

You can read the official docs for Asp.Net-Core globalization and localization.

Additionally, I wrote some articles describing localization in detail, see Developing Multicultural Web Application.

---

how can i show Validation in Arabic in most easy & simple way in ASP.Net core

If you are looking for a fast and easy way you can use LazZiya.ExpressLocalization nuget package, it offers very simple way for all localization setup:

//add reference to :
using LazZiya.ExpressLocalization;

//setup express localization under ConfigureServices method:
public void ConfigureServices(IServiceCollection services)
{
    //other configuration settings....

    var cultures = new CultureInfo[]
    {
        new CultureInfo("en"),
        new CultureInfo("tr"),
        new CultureInfo("ar")
    };

    services.AddRazorPages()
        //ExpressLocalizationResource and ViewLocalizationResource are available in :
        // https://github.com/LazZiya/ExpressLocalizationSample
        .AddExpressLocalization<ExpressLocalizationResource, ViewLocalizationResource>(
            exOps =>
            {
                exOps.ResourcesPath = "LocalizationResources";
                exOps.RequestLocalizationOptions = ops =>
                {
                    ops.SupportedCultures = cultures;
                    ops.SupportedUICultures = cultures;
                    ops.DefaultRequestCulture = new RequestCulture("en");
                };
            });
}

That is almost all what you need to setup the "express" localization. Here you can find a step by step tutorial for using ExpressLocalization and a sample github repository

Answer 2

Now you use this:

[Required]
[StringLength(16, ErrorMessage = "Identifier too long (16 character limit).")]
public string Identifier { get; set; }

But when you change to multilanguage you need to use like this:

[Required(ErrorMessageResourceType = typeof(MyProject.Resources.Starship),
      ErrorMessageResourceName = "IdentifierRequired")]
[StringLength(16, ErrorMessageResourceType = typeof(MyProject.Resources.Starship),
      ErrorMessageResourceName = "IdentifierLength")]
public string Identifier { get; set; }

In order to use this option, the classes associated with the referenced .resx resource files must be automatically generated. To do this, in the properties of the .resx file we must set its Custom tool property to ResXFileCodeGenerator or PublicResXFileCodeGenerator.