NopCommerce为了语言的国际化，它支持多国家的语言，你可以系统在添加任意多个国家语言。我之前的文章NopCommerce源码架构详解--使用FluentValidation创建Model自定义Validator验证源码分析就有提高到过nop的-Localization多语言。今天我就来详细介绍一下Nop是怎么实现的Localization多语言本地化。

首先，来看看Nop中与语言相关的表。

Nop主要有两个表来存储语言，分别是LocaleStringResource（每个语言相关明细--资源字符串）和Language（语言种类）

LocaleStringResource表：

SELECT TOP 1000 [Id]
      ,[LanguageId]
      ,[ResourceName]
      ,[ResourceValue]
  FROM [LocaleStringResource]

Language表：

SELECT TOP 1000 [Id]
      ,[Name]
      ,[LanguageCulture]
      ,[UniqueseoCode]
      ,[FlagImageFileName]
      ,[Rtl]
      ,[LimitedToStores]
      ,[DefaultCurrencyId]
      ,[Published]
      ,[DisplayOrder]
  FROM [Language]

接下来我们来通过一个验证提示信息类BlogPostValidator来看看这个多语言是怎么实现的?Nop的验证Validator可以参考：NopCommerce源码架构详解--使用FluentValidation创建Model自定义Validator验证源码分析

BlogPostValidator.cs：

public class BlogPostValidator : AbstractValidator<BlogPostModel>
{
	public BlogPostValidator(ILocalizationService localizationService)
	{
		RuleFor(x => x.Title)
			.NotEmpty()
			.WithMessage(localizationService.GetResource("Admin.ContentManagement.Blog.BlogPosts.Fields.Title.Required"));

		RuleFor(x => x.Body)
			.NotEmpty()
			.WithMessage(localizationService.GetResource("Admin.ContentManagement.Blog.BlogPosts.Fields.Body.Required"));
	}
}

接口ILocalizationService的真正实现类是Nop.Services.Localization.LocalizationService，其中里面的方法GetResource为：

public virtual string GetResource(string resourceKey, int languageId,
            bool logIfNotFound = true, string defaultValue = "", bool returnEmptyIfNotFound = false)
{
	string result = string.Empty;
	if (resourceKey == null)
		resourceKey = string.Empty;
	resourceKey = resourceKey.Trim().ToLowerInvariant();
	if (_localizationSettings.LoadAllLocaleRecordsOnStartup)
	{
		//load all records (we know they are cached)
		var resources = GetAllResourceValues(languageId);
		if (resources.ContainsKey(resourceKey))
		{
			result = resources[resourceKey].Value;
		}
	}
	else
	{
		//gradual loading
		string key = string.Format(LOCALSTRINGRESOURCES_BY_RESOURCENAME_KEY, languageId, resourceKey);
		string lsr = _cacheManager.Get(key, () =>
		{
			var query = from l in _lsrRepository.Table
						where l.ResourceName == resourceKey
						&& l.LanguageId == languageId
						select l.ResourceValue;
			return query.FirstOrDefault();
		});

		if (lsr != null) 
			result = lsr;
	}
	if (String.IsNullOrEmpty(result))
	{
		if (logIfNotFound)
			_logger.Warning(string.Format("Resource string ({0}) is not found. Language ID = {1}", resourceKey, languageId));
		
		if (!String.IsNullOrEmpty(defaultValue))
		{
			result = defaultValue;
		}
		else
		{
			if (!returnEmptyIfNotFound)
				result = resourceKey;
		}
	}
	return result;
}

public virtual string GetResource(string resourceKey)
{
	if (_workContext.WorkingLanguage != null)
		return GetResource(resourceKey, _workContext.WorkingLanguage.Id);
	
	return "";
}

接口IWorkContext真正实现类是Nop.Web.Framework.WebWorkContext，里面有一个获取语言的属性。

public virtual Language WorkingLanguage
{
	get
	{
		if (_cachedLanguage != null)
			return _cachedLanguage;
		
		Language detectedLanguage = null;
		if (_localizationSettings.SeoFriendlyUrlsForLanguagesEnabled)
		{
			//从URL中获取语言
			detectedLanguage = GetLanguageFromUrl();
		}
		if (detectedLanguage == null && _localizationSettings.AutomaticallyDetectLanguage)
		{
			//get language from browser settings
			//but we do it only once
			if (!this.CurrentCustomer.GetAttribute<bool>(SystemCustomerAttributeNames.LanguageAutomaticallyDetected, 
				_genericAttributeService, _storeContext.CurrentStore.Id))
			{
				detectedLanguage = GetLanguageFromBrowserSettings();
				if (detectedLanguage != null)
				{
					_genericAttributeService.SaveAttribute(this.CurrentCustomer, SystemCustomerAttributeNames.LanguageAutomaticallyDetected,
						 true, _storeContext.CurrentStore.Id);
				}
			}
		}
		if (detectedLanguage != null)
		{
			//the language is detected. now we need to save it
			if (this.CurrentCustomer.GetAttribute<int>(SystemCustomerAttributeNames.LanguageId,
				_genericAttributeService, _storeContext.CurrentStore.Id) != detectedLanguage.Id)
			{
				_genericAttributeService.SaveAttribute(this.CurrentCustomer, SystemCustomerAttributeNames.LanguageId,
					detectedLanguage.Id, _storeContext.CurrentStore.Id);
			}
		}

		var allLanguages = _languageService.GetAllLanguages(storeId: _storeContext.CurrentStore.Id);
		//find current customer language
		var languageId = this.CurrentCustomer.GetAttribute<int>(SystemCustomerAttributeNames.LanguageId,
			_genericAttributeService, _storeContext.CurrentStore.Id);
		var language = allLanguages.FirstOrDefault(x => x.Id == languageId);
		if (language == null)
		{
			//如果没有指定语言，默认返回系统中的第一种语言
			language = allLanguages.FirstOrDefault();
		}
		if (language == null)
		{
			//it not specified, then return the first found one
			language = _languageService.GetAllLanguages().FirstOrDefault();
		}

		//cache
		_cachedLanguage = language;
		return _cachedLanguage;
	}
	set
	{
		var languageId = value != null ? value.Id : 0;
		_genericAttributeService.SaveAttribute(this.CurrentCustomer,
			SystemCustomerAttributeNames.LanguageId,
			languageId, _storeContext.CurrentStore.Id);

		//reset cache
		_cachedLanguage = null;
	}
}