ASP.NET MVC：实现我们自己的视图引擎
<p >在ASP.NET MVC的一个开源项目MvcContrib中，为我们提供了几个视图引擎，例如NVelocity, Brail, NHaml, XSLT。那么如果我们想在ASP.NET MVC中实现我们自己的一个视图引擎，我们应该要怎么做呢？<p ><p >我们知道呈现视图是在Controller中通过传递视图名和数据到RenderView()方法来实现的。好，我们就从这里下手。我们查看一下ASP.NET MVC的源代码，看看RenderView()这个方法是如何实现的：<p ><CENTER><ccid_nobr><table width="400" border="1" cellspacing="0" cellpadding="2"bordercolorlight = "black" bordercolordark = "#FFFFFF" align="center"><tr><td bgcolor="e6e6e6" class="code" ><pre><ccid_code>protected virtual void RenderView(string viewName, string masterName, object viewData) { ViewContext viewContext = new ViewContext(ControllerContext, viewName, masterName, viewData, TempData); ViewEngine.RenderView(viewContext);}//</ccid_code></pre></td></tr></table></ccid_nobr></CENTER><br><p >这是P2的源码，P3略有不同，原理差不多，从上面的代码我们可以看到，Controller中的RenderView()方法主要是将ControllerContext, viewName, masterName, viewData, TempData这一堆东西封装成ViewContext，然后把ViewContext传递给ViewEngine.RenderView(viewContext)。嗯，没错，我们这里要实现的就是ViewEngine的RenderView()方法。<p ><p >ASP.NET MVC为我们提供了一个默认的视图引擎，这个视图引擎叫做：WebFormsViewEngine. 从名字就可以看出，这个视图引擎是使用ASP.NET web forms来呈现的。在这里，我们要实现的视图引擎所使用的模板用HTML文件吧，简单的模板示例代码如下：<p ><CENTER><ccid_nobr><table width="400" border="1" cellspacing="0" cellpadding="2"bordercolorlight = "black" bordercolordark = "#FFFFFF" align="center"><tr><td bgcolor="e6e6e6" class="code" ><pre><ccid_code>＜!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"＞＜html xmlns=""http://www.w3.org/1999/xhtml"">http://www.w3.org/1999/xhtml" ＞＜head＞ ＜title＞自定义视图引擎示例＜/title＞＜/head＞＜body＞ ＜h1＞{$ViewData.Title}＜/h1＞ ＜p＞{$ViewData.Message}＜/p＞ ＜p＞The following fruit is part of a string array: {$ViewData.FruitStrings}＜/p＞ ＜p＞The following fruit is part of an object array: {$ViewData.FruitObjects.Name}＜/p＞ ＜p＞Here's an undefined variable: {$UNDEFINED}＜/p＞＜/body＞＜ ml＞</ccid_code></pre></td></tr></table></ccid_nobr></CENTER><br><p >下面马上开始我们的实现。首先，毫无疑问的，我们要创建一个ViewEngine，就命名为 SimpleViewEngine 吧，注意哦，ViewEngine要实现IViewEngine接口：<p ><CENTER><ccid_nobr><table width="400" border="1" cellspacing="0" cellpadding="2"bordercolorlight = "black" bordercolordark = "#FFFFFF" align="center"><tr><td bgcolor="e6e6e6" class="code" ><pre><ccid_code>public class SimpleViewEngine : IViewEngine { #region Private members IViewLocator _viewLocator = null; #endregion #region IViewEngine Members : RenderView() public void RenderView(ViewContext viewContext) { string viewLocation = ViewLocator.GetViewLocation (viewContext, viewContext.ViewName); if (string.IsNullOrEmpty(viewLocation)) { throw new InvalidOperationException(string.Format ("View {0} could not be found.", viewContext.ViewName)); } string viewPath = viewContext.HttpContext.Request.MapPath(viewLocation); string viewTemplate = File.ReadAllText(viewPath); //以下为模板解析 IRenderer renderer = new PrintRenderer(); viewTemplate = renderer.Render(viewTemplate, viewContext); viewContext.HttpContext.Response.Write(viewTemplate); } #endregion #region Public properties : ViewLocator public IViewLocator ViewLocator { get { if (this._viewLocator == null) { this._viewLocator = new SimpleViewLocator(); } return this._viewLocator; } set { this._viewLocator = value; } } #endregion }</ccid_code></pre></td></tr></table></ccid_nobr></CENTER><br><p align="center"><font color="FF0000" >1</font>2<span class="content01">下一页>></span></p></p>
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