How do I change languages in a Blazor server-side application?

Languages are changed by using localization in the Blazor server-side application. In the following example, the languages are changed from English to French and vice versa by clicking a button. 

[Program.cs]

builder.Services.AddLocalization(); 

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

var localizeOptions = new RequestLocalizationOptions() 

                .SetDefaultCulture("en-US") 

                .AddSupportedCultures("en-US", "fr-FR") 

                .AddSupportedUICultures("en-US", "fr-FR"); 

app.UseRequestLocalization(localizeOptions); 

app.MapControllers(); 
…

[Culture.cs]

. . .
using Microsoft.AspNetCore.Localization;
using Microsoft.AspNetCore.Mvc;
namespace BlazorAppLocale
{
    [Route("/[controller]")]
    [ApiController]
    public class Culture : ControllerBase
    {
        public ActionResult SetCulture()
        {
            IRequestCultureFeature culture = HttpContext.Features.Get<IRequestCultureFeature>();
            Response.Cookies.Append(
                CookieRequestCultureProvider.DefaultCookieName,
                CookieRequestCultureProvider.MakeCookieValue(
                    new RequestCulture(new string[] { "en-US", "fr-FR" }
                    .Where(option => option != culture.RequestCulture.Culture.Name)
                    .FirstOrDefault())));

            return Redirect("/");
        }
    }
}

Add the culture resource files in the Resources/Pages folder.

[Index.razor]

@page "/"

@inject Microsoft.Extensions.Localization.IStringLocalizer<Resource> locale

<h1>@locale["Hello World"]</h1>

@locale["Welcome to your new app."]

<SurveyPrompt Title="How is Blazor working for you?" />

Add the button for changing the language.

[MainLayout.razor]

@inject NavigationManager UriHelper

<div class="top-row px-4"> 
    <button class="btn btn-secondary" @onclick="OnSelected">Change Language</button>
</div>

@code {

    private void OnSelected()
    {
        UriHelper.NavigateTo("Culture", true);
    }
}

You can download the reference sample here.

Please refer to this link for more information.