> 说明

对于Asp.net Core MVC架构的Web程序，可使用MVC自身提供的国际化方法，实现对控制器、视图、数据注释内容的国际化处理。

> 实现

1、在Startup.cs中添加国际化服务

* 在ConfigureServices中添加配置，指定资源文件夹名称，添加支持的多语言文化，指定默认的语言

```C#
public void ConfigureServices(IServiceCollection services)
{
	#region 多语言支持
	services.AddLocalization(options => options.ResourcesPath = "Resources");

services.AddMvc()
		.AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)
		.AddDataAnnotationsLocalization();

services.Configure<RequestLocalizationOptions>(options =>
	{
		var supportedCultures = new List<CultureInfo>
		{
			new CultureInfo("zh-CN"),
			new CultureInfo("en-US"),
		};

options.DefaultRequestCulture = new RequestCulture("zh-CN");
		options.SupportedCultures = supportedCultures;
		options.SupportedUICultures = supportedCultures;
	});
	#endregion

services.AddControllersWithViews();
}
```

* 在Configure中添加多语言配置

```c#
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
	#region 多语言支持
	IList<CultureInfo> supportedCultures = new List<CultureInfo>
	{
		new CultureInfo("en-US"),
		new CultureInfo("zh-CN"),
	};
	app.UseRequestLocalization(new RequestLocalizationOptions
	{
		DefaultRequestCulture = new RequestCulture("zh-CN"),
		SupportedCultures = supportedCultures,
		SupportedUICultures = supportedCultures
	});
	#endregion
	
	......
```

2、添加多语言切换方法和视图页面

* 在HomeController.cs中添加多语言切换方法

```c#
[HttpPost]
public IActionResult SetLanguage(string culture, string returnUrl)
{
	Response.Cookies.Append(
		CookieRequestCultureProvider.DefaultCookieName,
		CookieRequestCultureProvider.MakeCookieValue(new RequestCulture(culture)),
		new CookieOptions { Expires = DateTimeOffset.UtcNow.AddYears(1) }
	);

return LocalRedirect(returnUrl);
}
```

* 在Views=>Shared中添加用于多语言切换操作的分部视图

_SelectLanguagePartial.cshtml

```html
@using Microsoft.AspNetCore.Builder
@using Microsoft.AspNetCore.Http.Features
@using Microsoft.AspNetCore.Localization
@using Microsoft.AspNetCore.Mvc.Localization
@using Microsoft.Extensions.Options

@inject IViewLocalizer Localizer
@inject IOptions<RequestLocalizationOptions> LocOptions

@{
    var requestCulture = Context.Features.Get<IRequestCultureFeature>();
    var cultureItems = LocOptions.Value.SupportedUICultures
    .Select(c => new SelectListItem { Value = c.Name, Text = c.DisplayName })
    .ToList();
    var returnUrl = string.IsNullOrEmpty(Context.Request.Path) ? "~/" : $"~{Context.Request.Path.Value}";
}

<div title="@Localizer[" Request culture provider:"] @requestCulture?.Provider?.GetType().Name">
    <form id="selectLanguage" asp-controller="Home" asp-action="SetLanguage" asp-route-returnUrl="@returnUrl"
        method="post" class="form-horizontal" role="form">
        <label asp-for="@requestCulture.RequestCulture.UICulture.Name">@Localizer["Language:"]</label>
        <select name="culture" onchange="this.form.submit();"
            asp-for="@requestCulture.RequestCulture.UICulture.Name" asp-items="cultureItems">
        </select>
    </form>
</div>
```

将此视图添加到_Layout.cshtml中，例如添加到脚注栏

```html
<footer class="border-top footer text-muted">
	<div class="row">
		<div class="col-md-6">
			© @System.DateTime.Now.Year - WebApplication1 - <a asp-area="" asp-controller="Home" asp-action="Privacy">Privacy</a>
		</div>
		<div class="col-md-6" text-right>
			@await Html.PartialAsync("_SelectLanguagePartial")
		</div>
	</div>
</footer>
```

3、添加多语言资源文件

* 在项目根路径下添加资源文件夹，名称与Startup.cs中配置的名称相同，这里为Resources文件夹

在Resources下创建Controllers和Views两个子文件夹，Views子文件夹里的路径与视图文件夹Views的路径对应，创建简体中文zh-CN和美国英语en-US的resx资源文件。例如以下几个资源路径

Resources=>Controllers=>HomeController.zh-CN.resx

Resources=>Controllers=>HomeController.en-US.resx

Resources=>Views=>Shared=>Layout.zh-CN.resx

Resources=>Views=>Shared=>Layout.en-US.resx

Resources=>Views=>Home=>Index.zh-CN.resx

Resources=>Views=>Home=>Index.en-US.resx

Resources=>Views=>Home=>Privacy.zh-CN.resx

Resources=>Views=>Home=>Privacy.en-US.resx

4、控制器内容的国际化

在控制器中，通过引入`IStringLocalizer`接口实现。`IStringLocalizer` 不要求在资源文件中存储默认语言字符串，开发针对本地化应用时无需在开发初期创建资源文件。 下面的代码演示如何针对本地化包装字符串“Hello!”，收集这些需要本地化的词条，添加到多语言资源文件中。

```c#
public class HomeController : Controller
{
	// 控制器代码的国际化支持
	private readonly IStringLocalizer<HomeController> _localizer;

public HomeController(IStringLocalizer<HomeController> localizer)
	{
		_localizer = localizer;
	}
	
	...
	
    // 一个演示方法
    public IActionResult Hello()
    {
    return Content(_localizer["Hello!"]);
    }
}
```

页面地址栏键入如下URL: https://localhost:44392/Home/Hello，显示内容将根据选择的语言自动切换。也可以在URL中附加文化参数，来观察显示语言的变化，如

https://localhost:44392/Home/Hello?culture=zh-CN 将切换为中文显示，

https://localhost:44392/Home/Hello?culture=en-US 将切换为英文显示。

5、视图页面内容的国际化

在视图中，通过引入`IViewLocalizer`接口实现。`IViewLocalizer`同样不要求在资源文件中存储默认语言字符串，开发针对本地化应用时无需在开发初期创建资源文件。收集这些需要本地化的词条，添加到多语言资源文件中。

```c#
@using Microsoft.AspNetCore.Mvc.Localization

@inject IViewLocalizer Localizer

@{
    ViewData["Title"] = Localizer["Home Page"];
}

<div class="text-center">
    <h1 class="display-4">@Localizer["Welcome"]</h1>
    <p>@Localizer["Learn about"] <a href="https://docs.microsoft.com/aspnet/core">@Localizer["building Web apps with ASP.NET Core"]</a>.</p>
</div>
```

6、DataAnnotations（数据注释）的国际化

DataAnnotations 错误消息已使用 `IStringLocalizer<T>` 本地化。 直接收集这些需要本地化的词条，添加到多语言资源文件中。

```C#
public class RegisterViewModel
{
    [Required(ErrorMessage = "The Email field is required.")]
    [EmailAddress(ErrorMessage = "The Email field is not a valid email address.")]
    [Display(Name = "Email")]
    public string Email { get; set; }

[Required(ErrorMessage = "The Password field is required.")]
    [StringLength(8, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
    [DataType(DataType.Password)]
    [Display(Name = "Password")]
    public string Password { get; set; }

[DataType(DataType.Password)]
    [Display(Name = "Confirm password")]
    [Compare("Password", ErrorMessage = "The password and confirmation password do not match.")]
    public string ConfirmPassword { get; set; }
}
```

![资源文件目录结构](http://img.blog.itpub.net/blog/2021/09/26/a7db71db2621e7e1.png?x-oss-process=style/bb "资源文件目录结构")

![中文页面](http://img.blog.itpub.net/blog/2021/09/26/47e9889f7ff0f393.png?x-oss-process=style/bb "中文页面")

![英文页面](http://img.blog.itpub.net/blog/2021/09/26/ff148df5632a7133.png?x-oss-process=style/bb "英文页面")

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Asp.net Core MVC 程序的国际化处理

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