Adding Razor keywords - asp.net-mvc

Question

What is the best process to extend the Razor view-engine to add additional keywords?
I'm not a fan of the dynamic ViewBag property, so for all of my pages I define both a strongly-typed ViewModel POCO, but also a strongly-typed ViewData object:
public abstract class BaseViewData<TModel,TController> : ViewDataDictionary<TModel>
(TController is specified to optionally allow strongly-typed callbacks to the parent Controller)
This is so I can have compile-time verified members, like String PageTitle (in a site-wide base class) and per-page members - it works in tandem with the ViewModel: the BaseViewData-subclass contains one-way data, and the ViewModel-class contains two-way data. This works great when you tweak the MSBuild system to precompile your views into the output assembly - no more .aspx or .cshtml files!
In ASP.NET MVC (using the WebForms view-engine) I have my own base ViewPage subclass:
public class ViewPage2<TViewModel,TViewData> : ViewPage<TModel> where TViewData : ViewDataDictionary<TModel> {
private TViewData _data;
public new TViewData ViewData {
get {
if( _data == null ) {
_data = (TViewData)base.ViewData;
}
return _data;
}
}
}
I recently brought this over to Razor, easily done:
public abstract class WebViewPage2<TViewModel,TViewData> : WebViewPage<TModel> where TData : ViewDataDictionary<TModel> {
// same ViewData property code as above
}
In the .cshtml files you can manually specify the base-class with the #inherits razor keyword - which requires the fully-qualified concrete generic type name - but alternatively you can omit #inherits and instead specify the #model keyword, which Razor will pass as the TModel argument to WebViewPage<TModel>.
As my base-class adds a second generic type argument, I'd rather not have to type out this ins my .cshtml files:
#inherits MyNamespace.WebViewPage2<MyOtherNameSpace.Views.FooViewModel,MyOtherNameSpace.Views.FooViewData>
...but instead do this:
Web.config
<system.web.webPages.razor>
<pages pageBaseType="MyNamespace.WebViewPage2">
...
MyPage.cshtml
#model FooViewModel
#data FooViewData
But this would require extending the Razor View-engine somehow - but this is non-obvious as it requires extending the Razor parser itself so it recognises #data TViewData and passes it as the second type argument.

Answer 1

You can implement an inheriting ViewClass like this (be careful with the namespace, it must not be changed):
namespace System.Web.Mvc {
public abstract class WebViewPage<TViewModel, TModel> : WebViewPage<TModel> where TViewModel : class {
private TViewModel _viewModel;
public TViewModel ViewModel {
get {
if (_viewModel == null) {
throw new InvalidOperationException("No ViewModel defined for this View.");
}
return _viewModel;
}
set { _viewModel = value; }
}
public override void InitHelpers() {
base.InitHelpers();
if (this.ViewBag.ViewModel == null) {
// No ViewModel defined => set null.
}
else if (!(this.ViewBag.ViewModel is TViewModel)) {
throw new InvalidOperationException(string.Format("The specified ViewModel value is of type '{0}' and must be of type '{1}'.", this.ViewBag.ViewModel.GetType(), typeof(TViewModel)));
} else {
_viewModel = this.ViewBag.ViewModel;
}
}
}
}
Then you dont have to change the web.config or anything else and can instantiate the view like this:
#model ViewModelType, (Input?)ModelType
The typed ViewModel (Type would by ViewModelType) is then available in the view via #ViewModel.
The Model of type (Input)ModelType is still available via #Model like it always was.