.NET Nancy 详解(三) Respone 和 ViewEngine

我们在ASP.NET MVC中可以返回各种类型的ActionResult(以下图片来自于园友--待补。。)

在Nancy 中本着简单粗暴的原则，使用方式略有不同。这期我们使用的版本是Nancy的第一个tag version 0.0.2.0。

public MainModule(IRouteCacheProvider routeCacheProvider){Get["/"] = x => {return View.Razor("~/views/routes.cshtml", routeCacheProvider.GetCache());};// TODO - implement filtering at the RouteDictionary GetRoute levelGet["/filtered", r => true] = x => {return "This is a route with a filter that always returns true.";};Get["/filtered", r => false] = x => {return "This is also a route, but filtered out so should never be hit.";};Get["/test"] = x => {return "Test";};Get["/static"] = x => {return View.Static("~/views/static.htm");};Get["/razor"] = x => {var model = new RatPack { FirstName = "Frank" };return View.Razor("~/views/razor.cshtml", model);};Get["/ndjango"] = x => {var model = new RatPack { FirstName = "Michael" };return View.Django("~/views/ndjango.django", model);};Get["/spark"] = x => {var model = new RatPack { FirstName = "Bright" };return View.Spark("~/views/spark.spark", model);};Get["/json"] = x => {var model = new RatPack { FirstName = "Andy" };return Response.AsJson(model);};Get["/xml"] = x => {var model = new RatPack { FirstName = "Andy" };return Response.AsXml(model);};}

这里我们看到所有类型的返回还是储存在RouteDictionary中,依次为返回Razor View,string,static file,Django View,Spark View,Json,Xml......实际上也是用了一个ViewResult的类，因为只是执行不同的Action，所以只需要一个类表示。

public class ViewResult 
{public ViewResult(IView view, string location){this.View = view;this.Location = location;}public string Location { get; private set; }public IView View { get; private set; }public void Execute(Stream stream){// The caller needs to close the stream.var writer = new StreamWriter(stream);View.Writer = writer;View.Execute();writer.Flush();}

先从居家旅游必备的返回静态文件的例子开始：

public static Action<Stream> Static(this IViewEngine engine, string virtualPath){return stream => {var path = HostingEnvironment.MapPath(virtualPath);using (var reader = new StreamReader(path)){using(var writer = new StreamWriter(stream)){writer.Write(reader.ReadToEnd());writer.Flush();}}};}，

可以看到这里采用的是扩展IViewEngine，返回的是一个对Stream的Action。比较简单就不展开细说了。

对于xml 和 json 的返回值处理方法类似，这里就合并在一起作了类似的处理。

public static class FormatterExtensions
{public static Response AsJson<TModel>(this IResponseFormatter formatter, TModel model){return new JsonResponse<TModel>(model);}public static Response AsXml<TModel>(this IResponseFormatter formatter, TModel model){return new XmlResponse<TModel>(model);}public static Response Image(this IResponseFormatter formatter, string imagePath){return new ImageResponse(imagePath);}
}

Nancy支持的ViewEngine很多，以Razor为例来看。

    public MainModule(IRouteCacheProvider routeCacheProvider){Get["/"] = x => {return View.Razor("~/views/routes.cshtml", routeCacheProvider.GetCache());};}

这里的路径是"~/views/routes.cshtml"，首先找到实际的磁盘路径：

public ViewLocationResult GetTemplateContents(string viewTemplate){var path = HostingEnvironment.MapPath(viewTemplate);return new ViewLocationResult(path, new StreamReader(path));}

这里的返回值是该文件的一个StreamReader，然后传递给我们的View Compiler。

var result = ViewTemplateLocator.GetTemplateContents(viewTemplate);
var view = ViewCompiler.GetCompiledView<TModel>(result.Contents);RazorEngine和CodeDom。

这里结合使用了RazorEngine和CodeDom，这两个东西本身比较大，这里只是告诉大家有这么个东西，能够做什么。RazorEngine开源项目地址:https://github.com/Antaris/RazorEngine 。

举个简单的例子：

string template = "Hello @Model.Name, welcome to RazorEngine!";
var result =Engine.Razor.RunCompile(template, "templateKey", null, new { Name = "World" });

CodeDomProvider用来生成中间代码。CodeDom是.NET 的一项依据模板生成代码的技术，这方面园友有不少文章(比如说这个:http://www.cnblogs.com/whitewolf/archive/2010/06/19/1760708.html)。可以看到生成的临时文件内容如下，最终会编译并执行最终输出我们需要的stream。