Controller 提供了众多的方法让我们返回各种类型的 ActionResult。
1. View
最常用的一种，用于返回一个 "标准" 页面。
protected internal virtual ViewResult View(string viewName, string masterName, object model){ if (model != null) { base.ViewData.Model = model; } return new ViewResult{ ViewName = viewName, MasterName = masterName, ViewData = base.ViewData, TempData = base.TempData};}public class ViewResult : ViewResultBase{ protected override ViewEngineResult FindView(ControllerContext context) { ViewEngineResult result = ViewEngineCollection.FindView(context, ViewName, MasterName); if (result.View != null) { return result; } ... }}
这个页面默认是 ViewPage，也可以是我们自己定义的其它模板引擎页面。
MVC 还提供了强类型的 ViewPage<TModel>。
public class User{ public string Name { get; set; } public int Age { get; set; }}public class TestController : Controller{ public ActionResult Index() { ViewData["message"] = "Hello, World!"; var model = new User { Name = "Tom", Age = 13 }; return View(model); }}
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<Learn.MVC.Controllers.User>" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title></head><body> Name: <%= Model.Name %>; Age: <%= Model.Age %></body></html>
在 WebForm 时代，我们就已经习惯了将一个页面分解成多个 UserControl，现在我们依然可以这么做。htmlHelper 专门提供了 RenderPartial 扩展方法，从当前视图目录(Views\xxx)下载入 .ascx 页面。
public static class RenderPartialExtensions{ public static void RenderPartial(this HtmlHelper htmlHelper, partialViewName, model, viewData) { htmlHelper.RenderPartialInternal(partialViewName, viewData, model, ViewEngines.Engines); }}public class HtmlHelper{ internal virtual void RenderPartialInternal(string partialViewName, ViewDataDictionary viewData, object model, ViewEngineCollection viewEngineCollection) { ... ViewDataDictionary newViewData = null; if (model == null) { if (viewData == null)newViewData = new ViewDataDictionary(ViewData); elsenewViewData = new ViewDataDictionary(viewData); } else { if (viewData == null)newViewData = new ViewDataDictionary(model); elsenewViewData = new ViewDataDictionary(viewData) { Model = model }; } ViewContext newViewContext = new ViewContext(ViewContext, ViewContext.View, newViewData, ViewContext.TempData); IView view = FindPartialView(newViewContext, partialViewName, viewEngineCollection); view.Render(newViewContext, ViewContext.HttpContext.Response.Output); } internal static IView FindPartialView(viewContext, partialViewName, viewEngineCollection) { ViewEngineResult result = viewEngineCollection.FindPartialView(viewContext, partialViewName); if (result.View != null) { return result.View; } ... }}
RenderPartialInternal 调用 FindParitialView 从视图引擎中载入 .ascx，同时将当前的环境参数传递给它。也就是说 RenderPartial 只是一种视图级别的行为，并不会再次触发 Controller Action 操作，这点要和 Controller.PartialView() 区别开来。
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<Learn.MVC.Controllers.User>" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title></head><body> Name: <%= Model.Name %>; Age: <%= Model.Age %> <br /> <% Html.RenderPartial("Part"); %></body></html>
Part.ascx
<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Learn.MVC.Controllers.User>" %><%= ViewData["message"] %> <br /><%= Model.Name %>
2. Content
Content 用于输出(Response.Write) "静态" 片段。
protected internal virtual ContentResult Content(content, contentType, contentEncoding){ return new ContentResult { Content = content, ContentType = contentType, ContentEncoding = contentEncoding };}public class ContentResult : ActionResult{ public string Content { get; set; } public override void ExecuteResult(ControllerContext context) { ... HttpResponseBase response = context.HttpContext.Response; if (!String.IsNullOrEmpty(ContentType)) { response.ContentType = ContentType; } if (ContentEncoding != null) { response.ContentEncoding = ContentEncoding; } if (Content != null) { response.Write(Content); } }}
看看和 jQuery 的配合使用。
public class TestController : Controller{ public ActionResult Index() { return View(); } public ActionResult Part() { return Content("<a href=\"\">Q.yuhen</a>"); }}
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title> <script src="/Scripts/jquery-1.3.1.min.js" type="text/javascript"></script> <script type="text/javascript"> $(function() { $("#div1").load("/test/part"); }); </script></head><body> <div id="div1"> </div></body></html>
3. PartialView
Controller.PartialView() 和 HtmlHelper.RenderPartial() 的不同之处在于前者是再次执行 ActionInvoke 并返回一个 ActionResult 结果，后者只是使用现有的 ViewContext 显示一个视图片段。而与 Controller.Content() 的区别是 PartialView() 使用视图引擎输出一个 "动态" 的 ascx 结果。
protected internal virtual PartialViewResult PartialView(string viewName, object model){ if (model != null) { ViewData.Model = model; } return new PartialViewResult { ViewName = viewName, ViewData = ViewData, TempData = TempData };}public class PartialViewResult : ViewResultBase{ protected override ViewEngineResult FindView(ControllerContext context) { ViewEngineResult result = ViewEngineCollection.FindPartialView(context, ViewName); if (result.View != null) { return result; }... }}
和 Content() 一样，我们通常将其和 jQuery 等 Ajax 框架配合使用。
public class TestController : Controller{ public ActionResult Index() { return View(); } public ActionResult Part() { ViewData["time"] = DateTime.Now; var model = new User { Name = "Tom", Age = 13 }; return PartialView(model); }}
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title> <script src="/Scripts/jquery-1.3.1.min.js" type="text/javascript"></script> <script type="text/javascript"> $(function() { $("#div1").load("/test/part"); }); </script></head><body> <div id="div1"> </div></body></html>
Part.ascx
<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<Learn.MVC.Controllers.User>" %><%= ViewData["time"] %> <br /><%= Model.Name %>; <%= Model.Age %>
4. Redirect / RedirectToAction / RedirectToRoute
Controller 提供了几种方式，让我们在不同的 Action 之间进行跳转。
public class MvcApplication : System.Web.HttpApplication{ public static void RegisterRoutes(RouteCollection routes) { ... routes.MapRoute ( "Test2", "Test/T2/{name}/{age}", new { controller = "Test", action = "T2", name = "", age = 0 } ); ... }}
方法1:
Redirect() 直接用 Response.Redirect() 完成 url 跳转。
public class TestController : Controller{ public ActionResult Index() { return Redirect("/Test/T2/Tom/23"); } public ActionResult T2(User user) { return Content(user.Name); }}
相关细节：
protected internal virtual RedirectResult Redirect(string url){ ... return new RedirectResult(url);}public class RedirectResult : ActionResult{ public override void ExecuteResult(ControllerContext context) { ... string destinationUrl = UrlHelper.Content(Url, context.HttpContext); context.HttpContext.Response.Redirect(destinationUrl, false /* endResponse */); }}
方法2:
RedirectToAction() 直接使用 Action Name 进行跳转。
public class TestController : Controller{ public ActionResult Index() { return RedirectToAction("T2", new { name = "Tom", age = 23 }); } public ActionResult T2(User user) { return Content(user.Name); }}
如果目标 Action 不在当前 Controller 类，则可以指定目标 Controller Name。
return RedirectToAction("T2", new { controller="Test2", name = "Tom", age = 23 });
相关细节：
protected internal virtual RedirectToRouteResult RedirectToAction(string actionName,string controllerName, RouteValueDictionary routeValues){ RouteValueDictionary mergedRouteValues; if (RouteData == null) { mergedRouteValues = RouteValuesHelpers.MergeRouteValues(actionName, controllerName, null, routeValues, true /* includeImplicitMvcValues */); } else { mergedRouteValues = RouteValuesHelpers.MergeRouteValues(actionName, controllerName, RouteData.Values, routeValues, true /* includeImplicitMvcValues */); } return new RedirectToRouteResult(mergedRouteValues);}public class RedirectToRouteResult : ActionResult{ public override void ExecuteResult(ControllerContext context) { ... string destinationUrl = UrlHelper.GenerateUrl(RouteName, null /* actionName */, null /* controllerName */, RouteValues, Routes, context.RequestContext, false /* includeImplicitMvcValues */); ... context.HttpContext.Response.Redirect(destinationUrl, false /* endResponse */); }}
可以看到 RedirectToRouteResult.ExecuteResult 中使用 Route 相关信息拼接成目标 Url 后进行跳转。
方法3:
RedirectToRoute() 则是直接用 MapRoute 时定义的 Route Name 进行跳转。
public class TestController : Controller{ public ActionResult Index() { return RedirectToRoute("Test2", new { name = "Tom", age = 23 }); }}
相关细节：
protected internal virtual RedirectToRouteResult RedirectToRoute(string routeName, RouteValueDictionary routeValues){ return new RedirectToRouteResult(routeName, RouteValuesHelpers.GetRouteValues(routeValues));}
执行过程和 RedirectToAction() 相同。
5. Json
Json() 在编写 Ajax 时非常有用，可以将 Entity 等对象序列化成 JSON 格式供 Javascript 使用。
public class TestController : Controller{ public ActionResult Index() { return View(); } public ActionResult GetUser(string name) { var user = new User { Name = name, Age = 23 }; return Json(user); }}
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title> <script src="/Scripts/jquery-1.3.1.min.js" type="text/javascript"></script> <script type="text/javascript"> $(function() { $("#btnTest").click(function() {$.getJSON("/Test/GetUser", { name: "Tom" }, function(json){ alert(json.Name + ";" + json.Age);}); }); }); </script></head><body> <input type="button" id="btnTest" value="Test" /></body></html>
很好用，不是吗？看看相关细节。
protected internal virtual JsonResult Json(object data, string contentType, Encoding contentEncoding){ return new JsonResult { Data = data, ContentType = contentType, ContentEncoding = contentEncoding };}public class JsonResult : ActionResult{ public override void ExecuteResult(ControllerContext context) { ... if (Data != null) { JavaScriptSerializer serializer = new JavaScriptSerializer(); response.Write(serializer.Serialize(Data)); } }}
使用 System.Web.Script.Serialization.JavaScriptSerializer 完成 JSON 序列化操作，也就是说我们还可以用 ScriptIgnoreAttribute 排除某些属性。
6. Javascript
某些时候，我们需要根据一些逻辑判断来载入执行不同的 Javascript 代码。
public class TestController : Controller{ public ActionResult Index() { return View(); } public ActionResult GetJs(int id) { switch (id) { case 1:return JavaScript("alert('Hello, C#!');"); case 2:return JavaScript("alert('Hello, MVC!');"); default:return null; } }}
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title> <script src="/Scripts/jquery-1.3.1.min.js" type="text/javascript"></script> <script type="text/javascript"> $(function() { $("#btnTest").click(function() {var id = $("#txtId").val();$.getScript("/Test/GetJs/" + id); }); }); </script></head><body> <input type="text" id="txtId" value="1" /> <input type="button" id="btnTest" value="Test" /></body></html>
只是这种做法，似乎将 View 和 Controller 的耦合加大了…… 还不如直接用 Javascript 来处理这些。
protected internal virtual JavaScriptResult JavaScript(string script){ return new JavaScriptResult { Script = script };}public class JavaScriptResult : ActionResult{ public override void ExecuteResult(ControllerContext context) { ... HttpResponseBase response = context.HttpContext.Response; response.ContentType = "application/x-javascript"; if (Script != null) { response.Write(Script); } }}
7. File (Download / Upload)
File() 提供了 Download 功能。
public class TestController : Controller{ public ActionResult Index() { return View(); } public ActionResult Download(int id) { var filename = String.Format("~/Content/Download/{0}.rar", id); var fileDownloadName = String.Format("{0}.rar", id); return File(filename, "application/octet-stream", fileDownloadName); }}
当我们在浏览器请求 "/Test/Download/1" 是就会打开下载窗口，同时给出了保存文件名。
protected internal virtual FileContentResult File(byte[] fileContents, contentType, fileDownloadName){ return new FileContentResult(fileContents, contentType) { FileDownloadName = fileDownloadName };}public abstract class FileResult : ActionResult{ public override void ExecuteResult(ControllerContext context) { ... HttpResponseBase response = context.HttpContext.Response; response.ContentType = ContentType; ... WriteFile(response); } protected abstract void WriteFile(HttpResponseBase response);}public class FileContentResult : FileResult{ protected override void WriteFile(HttpResponseBase response) { response.OutputStream.Write(FileContents, 0, FileContents.Length); }}
文件上传是另一个常用的 Web 应用。
public class TestController : Controller{ public ActionResult Index() { return View(); } public ActionResult Upload(HttpPostedFileBase file) { var filename = Server.MapPath("~/Content/Upload/" + Path.GetFileName(file.FileName)); file.SaveAs(filename); return null; }}
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title></head><body> <form action="/Test/Upload" enctype="multipart/form-data" method="post"> <input type="file" name="file" /> <input type="submit" name="upload" /> </form></body></html>
MVC 提供了一个 HttpPostedFileBaseModelBinder 将 Request.Files 的信息直接映射给 Action 同名参数。
public class HttpPostedFileBaseModelBinder : IModelBinder{ public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) { ... HttpPostedFileBase theFile = controllerContext.HttpContext.Request.Files[bindingContext.ModelName]; // case 1: there was no <input type="file" ... /> element in the post if (theFile == null) { return null; } // case 2: there was an <input type="file" ... /> element in the post, but it was left blank if (theFile.ContentLength == 0 && String.IsNullOrEmpty(theFile.FileName)) { return null; } // case 3: the file was posted return theFile; }}
看看一次上传多个文件的演示。
public class TestController : Controller{ public ActionResult Index() { return View(); } public ActionResult Upload(HttpPostedFileBase file1, HttpPostedFileBase file2) { var html = String.Format("{0}:{1}<br />{2}:{3}", file1.FileName, file1.InputStream.Length, file2.FileName, file2.InputStream.Length); return Content(html); }}
Index.aspx
<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %><html xmlns="/1999/xhtml"><head runat="server"> <title>Index</title></head><body> <form action="/Test/Upload" enctype="multipart/form-data" method="post"> <input type="file" name="file1" /> <input type="file" name="file2" /> <input type="submit" name="upload" /> </form></body></html>
[最后修改
