调试Razor从哪里开始
使用ASP.NET MVC时，我们知道，要使用Views中的视图，需要在Action中写
return View();
这个方法返回的返回值是一个 ViewResult，进入这个类，继承了父类ViewResultBase后只写了MasterName属性和FindView方法。
不过已经开始看到到ViewEngine的踪影了。
protected override ViewEngineResult FindView(ControllerContext context) {
ViewEngineResult result = ViewEngineCollection.FindView(context, ViewName, MasterName);
...;
}
跟进ViewEngineCollection.FindView去看看。
来到了ViewEngineCollection类，这是一个实现了Collection<IViewEngine>的类。
public virtual ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName) {
if (controllerContext == null ) {
throw new ArgumentNullException( "controllerContext" );
}
if ( string .IsNullOrEmpty(viewName)) {
throw new ArgumentException(MvcResources.Common_NullOrEmpty, "viewName" );
}
return Find(e => e.FindView(controllerContext, viewName, masterName, true ),
e => e.FindView(controllerContext, viewName, masterName, false ));
}
很简单的一个方法，跟进去
private ViewEngineResult Find(Func<IViewEngine, ViewEngineResult> cacheLocator, Func<IViewEngine, ViewEngineResult> locator) {
// First, look up using the cacheLocator and do not track the searched paths in non-matching view engines
// Then, look up using the normal locator and track the searched paths so that an error view engine can be returned
return Find(cacheLocator, trackSearchedPaths: false )
?? Find(locator, trackSearchedPaths: true );
}
private ViewEngineResult Find(Func<IViewEngine, ViewEngineResult> lookup, bool trackSearchedPaths) {
// Returns
// 1st result
// OR list of searched paths (if trackSearchedPaths == true)
// OR null
ViewEngineResult result;
List< string > searched = null ;
if (trackSearchedPaths) {
searched = new List< string >();
}
foreach (IViewEngine engine in CombinedItems) {
if (engine != null ) {
result = lookup(engine);
if (result.View != null ) {
return result;
}
if (trackSearchedPaths) {
searched.AddRange(result.SearchedLocations);
}
}
}
if (trackSearchedPaths) {
// Remove duplicate search paths since multiple view engines could have potentially looked at the same path
return new ViewEngineResult(searched.Distinct().ToList());
}
else {
return null ;
}
}
乍一看，又是for又是if、else的有点不知所措，其实仔细一看结合上面的Find参数就能找到黄色加亮的几句代码关键代码。
是遍历了注册ViewEngine集合，调用ViewEngine各自的FindView，谁能找到View，就用谁。
那么遍历的ViewEngine集合怎么来的呢？要回到ViewResult的父类ViewResultBase中去看。
public ViewEngineCollection ViewEngineCollection {
get {
return _viewEngineCollection ?? ViewEngines.Engines;
}
set {
_viewEngineCollection = value ;
}
}
如果没有定义那么就调用ViewEngines.Engines，这是一个很简单的静态类属性
public static class ViewEngines {
private readonly static ViewEngineCollection _engines = new ViewEngineCollection {
new WebFormViewEngine(),
new RazorViewEngine(),
};
public static ViewEngineCollection Engines {
get {
return _engines;
}
}
}
回到刚才的遍历，由于RazorViewEngine的构造函数中定义了以下格式，在Views文件夹中也创建了相应的文件，所以选择了RazorViewEngine。
AreaViewLocationFormats = new [] {
"~/Areas/{2}/Views/{1}/{0}.cshtml" ,
"~/Areas/{2}/Views/{1}/{0}.vbhtml" ,
"~/Areas/{2}/Views/Shared/{0}.cshtml" ,
"~/Areas/{2}/Views/Shared/{0}.vbhtml"
};
好了，终于找到了Razor。
分类: ASP.NET MVC
作者： Leo_wl
出处： http://www.cnblogs.com/Leo_wl/
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