ABP的语言切换

在ABP官网http://www.aspnetboilerplate.com/创建一个Multi Page Web Application项目并打开，在Web项目下可以找到一个Controllers/LayoutController.cs，里面有代码如下：

[ChildActionOnly]
public PartialViewResult LanguageSelection()
{
var model = new LanguageSelectionViewModel
{
CurrentLanguage = _localizationManager.CurrentLanguage,
Languages = _localizationManager.GetAllLanguages()
};

return PartialView("_LanguageSelection", model);
}

对，这段控制器代码对应于视图Views/Layout/_LanguageSelection.cshtml，用于页面右上角的语言切换：



控制器传给视图一个LanguageSelectionViewModel对象，用于展示当前默认使用的语言和下拉菜单中支持的语言。

观察上面的代码，就知道LanguageSelectionViewModel对象里的信息其实都是从LocalizationManager传递过来的。查看ABP的源码，信息的源头又可以追溯到ILocalizationConfiguration，原来，语言实际配置的代码放在Web项目的App_Start/某某WebModule.cs的PreInitialize方法里：

public override void PreInitialize()
{
//Add/remove languages for your application
Configuration.Localization.Languages.Add(new LanguageInfo("en", "English", "famfamfam-flag-england", true));
Configuration.Localization.Languages.Add(new LanguageInfo("tr", "Türkçe", "famfamfam-flag-tr"));
Configuration.Localization.Languages.Add(new LanguageInfo("zh-CN", "简体中文", "famfamfam-flag-cn"));

...
}

LanguageInfo构造函数的第三个参数为图标名，从_LanguageSelection视图可以看到：

<li><a href="/AbpLocalization/ChangeCulture?cultureName=@(language.Name)&returnUrl=@(Request.Url)"><i class="@language.Icon"></i> @language.DisplayName</a></li>

原来在这里使用了一组famfamfam国旗图标，官网：http://www.famfamfam.com/lab/icons/flags/

查看Web项目下的Content/flags/famfamfam-flags.css可以看到对这些国旗图标的定义：

[class^="famfamfam-flag"] {
display: inline-block;
width: 16px;
height: 11px;
line-height: 11px;
/* vertical-align: text-top; */
background-image: url("famfamfam-flags.png");
background-position: 0 0;
background-repeat: no-repeat;
}

.famfamfam-flag-zw { background-position: 0px 0px; width: 16px; height: 11px; }
.famfamfam-flag-zm { background-position: -16px 0px; width: 16px; height: 11px; }
.famfamfam-flag-za { background-position: 0px -11px; width: 16px; height: 11px; }
.famfamfam-flag-yt { background-position: -16px -11px; width: 16px; height: 11px; }
.famfamfam-flag-ye { background-position: -32px 0px; width: 16px; height: 11px; }
.famfamfam-flag-ws { background-position: -32px -11px; width: 16px; height: 11px; }
.famfamfam-flag-wf { background-position: 0px -22px; width: 16px; height: 11px; }
...

图标文件：



当我们切换语言时，提交的链接大概是这样的：
http://localhost:61754/AbpLocalization/ChangeCulture?cultureName=en&returnUrl=http://localhost:61754/
问题是，ChangeCulture控制器在哪？

查看ABP源码，可以找到Abp.Web.Mvc.Controllers.Localization.AbpLocalizationController类：

public class AbpLocalizationController : AbpController
{
[DisableAuditing]
public virtual ActionResult ChangeCulture(string cultureName, string returnUrl = "")
{
if (!GlobalizationHelper.IsValidCultureCode(cultureName))
{
throw new AbpException("Unknown language: " + cultureName + ". It must be a valid culture!");
}

Response.Cookies.Add(new HttpCookie("Abp.Localization.CultureName", cultureName) { Expires = Clock.Now.AddYears(2) });

if (Request.IsAjaxRequest())
{
return Json(new MvcAjaxResponse(), JsonRequestBehavior.AllowGet);
}

if (!string.IsNullOrWhiteSpace(returnUrl))
{
return Redirect(returnUrl);
}

return Redirect(Request.ApplicationPath);
}
}

一目了然，ABP把“当前所使用的语言”记录在cookies里了。

再回头翻查LocalizationManager类里定义的GetCurrentLanguage方法：

private LanguageInfo GetCurrentLanguage()
{
if (_configuration.Languages.IsNullOrEmpty())
{
throw new AbpException("No language defined in this application. Define languages on startup configuration.");
}

var currentCultureName = Thread.CurrentThread.CurrentUICulture.Name;

//Try to find exact match
var currentLanguage = _configuration.Languages.FirstOrDefault(l => l.Name == currentCultureName);
if (currentLanguage != null)
{
return currentLanguage;
}

//Try to find best match
currentLanguage = _configuration.Languages.FirstOrDefault(l => currentCultureName.StartsWith(l.Name));
if (currentLanguage != null)
{
return currentLanguage;
}

//Try to find default language
currentLanguage = _configuration.Languages.FirstOrDefault(l => l.IsDefault);
if (currentLanguage != null)
{
return currentLanguage;
}

//Get first one
return _configuration.Languages[0];
}

上面代码并没发现读取cookies的操作，再翻到ABP源码的Abp.Web.AbpWebApplication类，原来放到了Application_BeginRequest方法里读取：

protected virtual void Application_BeginRequest(object sender, EventArgs e)
{
var langCookie = Request.Cookies["Abp.Localization.CultureName"];
if (langCookie != null && GlobalizationHelper.IsValidCultureCode(langCookie.Value))
{
Thread.CurrentThread.CurrentCulture = new CultureInfo(langCookie.Value);
Thread.CurrentThread.CurrentUICulture = new CultureInfo(langCookie.Value);
}
}