我想根据当前的 UI 文化在运行时更改视图位置。如何使用默认的 Web 表单视图引擎实现这一点？
基本上我想知道如何用WebFormViewEngine 实现custom IDescriptorFilter 中的Spark 是什么。
是否有其他视图引擎可以让我在运行时控制视图位置？
编辑：我的 URL 应该看起来像 {lang}/{controller}/{action}/{id}。我不需要依赖语言的控制器，并且视图已使用资源进行本地化。然而，在某些语言中，很少有观点会有所不同。所以我需要告诉视图引擎首先查看特定于语言的文件夹。
【问题讨论】：
标签： .net asp.net-mvc viewengine
我相信解决方案是创建您自己的继承自 WebFormViewEngine 的 ViewEngine。在构造函数中，它应该从当前线程检查当前 UI 文化并添加适当的位置。只是不要忘记将它添加到您的视图引擎中。
这应该看起来像这样：
public class ViewEngine : WebFormViewEngine
{
public ViewEngine()
{
if (CultureIsX())
ViewLocationFormats = new string[]{"route1/controller.aspx"};
if (CultureIsY())
ViewLocationFormats = new string[]{"route2/controller.aspx"};
}
}
在 global.asax 中：
ViewEngines.Engines.Add(new ViewEngine());
【讨论】：
VirtualPathProviderViewEngine.GetPathFromGeneralName 必须更改为允许来自路由的附加参数。它不公开，这就是为什么你必须将GetPath、GetPathFromGeneralName、IsSpecificPath 复制到你自己的ViewEngine 实现中。
你是对的：这看起来像是一个完整的重写。我希望GetPathFromGeneralName 是公开的。
using System.Web.Mvc;
using System;
using System.Web.Hosting;
using System.Globalization;
using System.Linq;
namespace MvcLocalization
{
public class LocalizationWebFormViewEngine : WebFormViewEngine
{
private const string _cacheKeyFormat = ":ViewCacheEntry:{0}:{1}:{2}:{3}:";
private const string _cacheKeyPrefix_Master = "Master";
private const string _cacheKeyPrefix_Partial = "Partial";
private const string _cacheKeyPrefix_View = "View";
private static readonly string[] _emptyLocations = new string[0];
public LocalizationWebFormViewEngine()
{
base.ViewLocationFormats = new string[] {
"~/Views/{1}/{2}/{0}.aspx",
"~/Views/{1}/{2}/{0}.ascx",
"~/Views/Shared/{2}/{0}.aspx",
"~/Views/Shared/{2}/{0}.ascx" ,
"~/Views/{1}/{0}.aspx",
"~/Views/{1}/{0}.ascx",
"~/Views/Shared/{0}.aspx",
"~/Views/Shared/{0}.ascx"
};
}
private VirtualPathProvider _vpp;
public override ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache)
{
if (controllerContext == null)
throw new ArgumentNullException("controllerContext");
if (String.IsNullOrEmpty(viewName))
throw new ArgumentException( "viewName");
string[] viewLocationsSearched;
string[] masterLocationsSearched;
string controllerName = controllerContext.RouteData.GetRequiredString("controller");
string viewPath = GetPath(controllerContext, ViewLocationFormats, "ViewLocationFormats", viewName, controllerName, _cacheKeyPrefix_View, useCache, out viewLocationsSearched);
string masterPath = GetPath(controllerContext, MasterLocationFormats, "MasterLocationFormats", masterName, controllerName, _cacheKeyPrefix_Master, useCache, out masterLocationsSearched);
if (String.IsNullOrEmpty(viewPath) || (String.IsNullOrEmpty(masterPath) && !String.IsNullOrEmpty(masterName)))
{
return new ViewEngineResult(viewLocationsSearched.Union(masterLocationsSearched));
}
return new ViewEngineResult(CreateView(controllerContext, viewPath, masterPath), this);
}
private string GetPath(ControllerContext controllerContext, string[] locations, string locationsPropertyName, string name, string controllerName, string cacheKeyPrefix, bool useCache, out string[] searchedLocations)
{
searchedLocations = _emptyLocations;
if (String.IsNullOrEmpty(name))
return String.Empty;
if (locations == null || locations.Length == 0)
throw new InvalidOperationException();
bool nameRepresentsPath = IsSpecificPath(name);
string cacheKey = CreateCacheKey(cacheKeyPrefix, name, (nameRepresentsPath) ? String.Empty : controllerName);
if (useCache)
{
string result = ViewLocationCache.GetViewLocation(controllerContext.HttpContext, cacheKey);
if (result != null)
{
return result;
}
}
return (nameRepresentsPath) ?
GetPathFromSpecificName(controllerContext, name, cacheKey, ref searchedLocations) :
GetPathFromGeneralName(controllerContext, locations, name, controllerName, cacheKey, ref searchedLocations);
}
private string GetPathFromGeneralName(ControllerContext controllerContext, string[] locations, string name, string controllerName, string cacheKey, ref string[] searchedLocations)
{
string result = String.Empty;
searchedLocations = new string[locations.Length];
string language = controllerContext.RouteData.Values["lang"].ToString();
for (int i = 0; i < locations.Length; i++)
{
string virtualPath = String.Format(CultureInfo.InvariantCulture, locations[i], name, controllerName,language);
if (FileExists(controllerContext, virtualPath))
{
searchedLocations = _emptyLocations;
result = virtualPath;
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
break;
}
searchedLocations[i] = virtualPath;
}
return result;
}
private string CreateCacheKey(string prefix, string name, string controllerName)
{
return String.Format(CultureInfo.InvariantCulture, _cacheKeyFormat,
GetType().AssemblyQualifiedName, prefix, name, controllerName);
}
private string GetPathFromSpecificName(ControllerContext controllerContext, string name, string cacheKey, ref string[] searchedLocations)
{
string result = name;
if (!FileExists(controllerContext, name))
{
result = String.Empty;
searchedLocations = new[] { name };
}
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
return result;
}
private static bool IsSpecificPath(string name)
{
char c = name[0];
return (c == '~' || c == '/');
}
}
}
【讨论】：
1) 从 razor 视图引擎扩展类
public class LocalizationWebFormViewEngine : RazorViewEngine
2) 添加部分位置格式
public LocalizationWebFormViewEngine()
{
base.PartialViewLocationFormats = new string[] {
"~/Views/{2}/{1}/{0}.cshtml",
"~/Views/{2}/{1}/{0}.aspx",
"~/Views/{2}/Shared/{0}.cshtml",
"~/Views/{2}/Shared/{0}.aspx"
};
base.ViewLocationFormats = new string[] {
"~/Views/{2}/{1}/{0}.cshtml",
"~/Views/{2}/{1}/{0}.aspx",
"~/Views/{2}/Shared/{0}.cshtml",
"~/Views/{2}/Shared/{0}.aspx"
};
}
3) 创建局部视图渲染的覆盖方法
public override ViewEngineResult FindPartialView(ControllerContext controllerContext, String partialViewName, Boolean useCache)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
if (String.IsNullOrEmpty(partialViewName))
{
throw new ArgumentException("partialViewName");
}
string[] partialViewLocationsSearched;
string controllerName = controllerContext.RouteData.GetRequiredString("controller");
string partialPath = GetPath(controllerContext, PartialViewLocationFormats, "PartialViewLocationFormats", partialViewName, controllerName, _cacheKeyPrefix_Partial, useCache, out partialViewLocationsSearched);
return new ViewEngineResult(CreatePartialView(controllerContext, partialPath), this);}
}
【讨论】：
下面是一个没有重写的本地化视图引擎。
简而言之，引擎会将新位置插入到视图位置每次查找视图。引擎将使用两种字符语言来查找视图。所以如果当前语言是es（西班牙语），它会寻找~/Views/Home/Index.es.cshtml。
查看代码 cmets 了解更多详情。
更好的方法是覆盖视图位置的解析方式，但这些方法是不可覆盖的；也许在 ASP.NET MVC 5 中？
public class LocalizedViewEngine : RazorViewEngine
{
private string[] _defaultViewLocationFormats;
public LocalizedViewEngine()
: base()
{
// Store the default locations which will be used to append
// the localized view locations based on the thread Culture
_defaultViewLocationFormats = base.ViewLocationFormats;
}
public override ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache)
{
AppendLocalizedLocations();
return base.FindPartialView(controllerContext, partialViewName, useCache:fase);
}
public override ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache)
{
AppendLocalizedLocations();
returnbase.FindView(controllerContext, viewName, masterName, useCache:false);
}
private void AppendLocalizedLocations()
{
// Use language two letter name to identify the localized view
string lang = Thread.CurrentThread.CurrentUICulture.TwoLetterISOLanguageName;
// Localized views will be in the format "{action}.{lang}.cshtml"
string localizedExtension = string.Format(".{0}.cshtml", lang);
// Create an entry for views and layouts using localized extension
string view = "~/Views/{1}/{0}.cshtml".Replace(".cshtml", localizedExtension);
string shared = "~/Views/{1}/Shared/{0}".Replace(".cshtml", localizedExtension);
// Create a copy of the default view locations to modify
var list = _defaultViewLocationFormats.ToList();
// Insert the new locations at the top of the list of locations
// so they're used before non-localized views.
list.Insert(0, shared);
list.Insert(0, view);
base.ViewLocationFormats = list.ToArray();
}
}
【讨论】：
一个简单的解决方案是，在您的Appication_Start 中，从ViewEngines.Engines 集合中获取适当的ViewEngine，并更新其ViewLocationFormats 数组和PartialViewLocationFormats。没有hackery：默认情况下它是读/写的。
protected void Application_Start()
{
...
// Allow looking up views in ~/Features/ directory
var razorEngine = ViewEngines.Engines.OfType<RazorViewEngine>().First();
razorEngine.ViewLocationFormats = razorEngine.ViewLocationFormats.Concat(new string[]
{
"~/Features/{1}/{0}.cshtml"
}).ToArray();
...
// also: razorEngine.PartialViewLocationFormats if required
}
Razor 的默认looks like this：
ViewLocationFormats = new string[]
{
"~/Views/{1}/{0}.cshtml",
"~/Views/{1}/{0}.vbhtml",
"~/Views/Shared/{0}.cshtml",
"~/Views/Shared/{0}.vbhtml"
};
请注意，您可能还想更新PartialViewLocationFormats。
【讨论】：
CustomViewEngine overkill 方法