Users from various locations can do the following with a multilingual CRUD application:

  • See information in their native tongue
  • Get messages that are localized
  • Utilize the same API across cultural boundaries

This is frequently utilized in:

  • Platforms for online sales
  • Apps for banks
  • Portals for the government
  • Global SaaS offerings
1. Project Scenario (Real-World Example)
We will build a Product Management API that supports:
  • English (en-US)
  • French (fr-FR)
  • Arabic (ar-SA)
The API will:
  • Create products
  • Read products
  • Update products
  • Delete products
Return localized messages

2. Technologies Used
  • ASP.NET Core Web API
  • Localization (IStringLocalizer)
  • Resource files (.resx)
  • In-memory data (for simplicity)
  • JSON & XML formats
3. Enable Localization in ASP.NET Core
Program.cs Configuration
using Microsoft.AspNetCore.Localization;
using System.Globalization;

builder.Services.AddLocalization(options =>
{
options.ResourcesPath = "Resources";
});

builder.Services.AddControllers()
.AddXmlSerializerFormatters();

var supportedCultures = new[]
{
new CultureInfo("en-US"),
new CultureInfo("fr-FR"),
new CultureInfo("ar-SA")
};

app.UseRequestLocalization(new RequestLocalizationOptions
{
DefaultRequestCulture = new RequestCulture("en-US"),
SupportedCultures = supportedCultures,
SupportedUICultures = supportedCultures
});

app.MapControllers();
app.Run();

4. Product Model
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public decimal Price { get; set; }
}

5. Resource Files Structure
Create a Resources folder:
Resources/
└── Controllers.ProductsController.en-US.resx
└── Controllers.ProductsController.fr-FR.resx
└── Controllers.ProductsController.ar-SA.resx

Resource Keys & Values

English (en-US)

KeyValue
ProductAdded Product added successfully
ProductUpdated Product updated successfully
ProductDeleted Product deleted successfully
ProductNotFound Product not found

French (fr-FR)

KeyValue
ProductAdded Produit ajouté avec succès
ProductUpdated Produit mis à jour avec succès
ProductDeleted Produit supprimé avec succès
ProductNotFound Produit introuvable

6. Products Controller (Localized CRUD)

using Microsoft.Extensions.Localization;

[ApiController]
[Route("api/products")]
public class ProductsController : ControllerBase
{
    private static List<Product> products = new();
    private readonly IStringLocalizer<ProductsController> _localizer;

    public ProductsController(IStringLocalizer<ProductsController> localizer)
    {
        _localizer = localizer;
    }

    [HttpGet]
    public IActionResult GetAll()
    {
        return Ok(products);
    }

    [HttpPost]
    public IActionResult Create(Product product)
    {
        products.Add(product);
        return Ok(new
        {
            Message = _localizer["ProductAdded"],
            Data = product
        });
    }

    [HttpPut("{id}")]
    public IActionResult Update(int id, Product updated)
    {
        var product = products.FirstOrDefault(p => p.Id == id);
        if (product == null)
            return NotFound(_localizer["ProductNotFound"]);

        product.Name = updated.Name;
        product.Price = updated.Price;

        return Ok(_localizer["ProductUpdated"]);
    }

    [HttpDelete("{id}")]
    public IActionResult Delete(int id)
    {
        var product = products.FirstOrDefault(p => p.Id == id);
        if (product == null)
            return NotFound(_localizer["ProductNotFound"]);

        products.Remove(product);
        return Ok(_localizer["ProductDeleted"]);
    }
}

7. Testing with Different Languages
Create Product (English)
Request

POST /api/products
Accept-Language: en-US
Content-Type: application/json

{
  "id": 1,
  "name": "Laptop",
  "price": 1200
}

Response
{
  "message": "Product added successfully",
  "data": {
    "id": 1,
    "name": "Laptop",
    "price": 1200
  }
}

Create Product (French)
Header
Accept-Language: fr-FR

Response
{
  "message": "Produit ajouté avec succès",
  "data": {
    "id": 1,
    "name": "Laptop",
    "price": 1200
  }
}

Delete Product (Arabic)
Request
DELETE /api/products/1
Accept-Language: ar-SA

Response
"تم حذف المنتج بنجاح"

8. XML Request & Response Example
XML Request
POST /api/products
Content-Type: application/xml
Accept-Language: en-US

<Product>
  <Id>2</Id>
  <Name>Mouse</Name>
  <Price>25</Price>
</Product>

XML Response
<object>
  <Message>Product added successfully</Message>
  <Data>
    <Id>2</Id>
    <Name>Mouse</Name>
    <Price>25</Price>
  </Data>
</object>

9. How Culture Is Selected
ASP.NET Core checks (in order):
  • Query string (?culture=fr-FR)
  • Cookies
  • Accept-Language header