更新:看起来Technitium找到了另一种方法,这看起来更容易,至少在较新版本的ASP.NET MVC上.(复制他的评论如下)
我不确定这是否是ASP.NET MVC 3中的新功能,但是当我将Inherits属性从引用C#语法中的泛型转换为CLR语法时,标准
ViewPageParserFilter已正确解析泛型 -CustomViewTypeParserFilter不需要.使用Justin的例子,这意味着交换
<%@ Page Language="C#" MyNewProperty="From @Page directive!"
Inherits="JG.ParserFilter.CustomViewPage
至
<%@ Page Language="C#" MyNewProperty="From @Page directive!"`
Inherits="JG.ParserFilter.CustomViewPage`1[MvcApplication1.Models.FooModel]>
原答案如下:
好的,我解决了这个问题.这是一项非常有趣的练习,解决方案非常重要,但是一旦你第一次使用它就不会太难.
这是底层问题:ASP.NET页面解析器不支持泛型作为页面类型.
ASP.NET MVC解决这个问题的方法是欺骗底层页面解析器,使其认为页面不是通用的.他们通过构建自定义PageParserFilter和自定义FileLevelPageControlBuilder来实现此目的.解析器过滤器查找泛型类型,如果找到一个类型,则将其交换为非泛型ViewPage类型,以便ASP.NET解析器不会阻塞.然后,在页面编译生命周期的后期,他们的自定义页面构建器类将通用类型重新交换.
这是因为通用ViewPage类型派生自非泛型ViewPage,并且在(非泛型)基类上存在@Page指令中设置的所有有趣属性.因此,在@Page指令中设置属性时真正发生的是,这些属性名称是针对非泛型ViewPage基类进行验证的.
无论如何,这在大多数情况下都很好用,但不适用于你的,因为他们在其页面过滤器实现中将ViewPage硬编码为非泛型基类型,并且不提供更改它的简单方法.这就是为什么你在错误消息中看到ViewPage的原因,因为在ASP.NET交换ViewPage占位符和在编译之前交换通用ViewPage之间发生错误.
解决方法是创建您自己的以下版本:
页面解析器过滤器 - 这几乎是MVC源中ViewTypeParserFilter.cs的精确副本,唯一的区别是它引用了自定义ViewPage和页面构建器类型而不是MVC的
页面构建器 - 这与MVC源中的ViewPageControlBuilder.cs相同,但它将类放在您自己的命名空间中而不是它们的名称空间中.
直接从System.Web.Mvc.ViewPage(非泛型版本)派生自定义viewpage类.在这个新的非泛型类上粘贴任何自定义属性.
从#3派生一个泛型类,从ASP.NET MVC源代码的ViewPage实现中复制代码.
如果您还需要用户控件指令的自定义属性,请对用户控件(@Control)重复#2,#3和#4.
然后,您需要更改views目录(而不是主应用程序的web.config)中的web.config以使用这些新类型而不是MVC的默认类型.
我附上了一些代码示例,说明了它是如何工作的.非常感谢Phil Haack的文章,以帮助我理解这一点,虽然我不得不在MVC和ASP.NET源代码中进行大量探索,以便真正理解它.
首先,我将从web.config中所需的web.config更改开始:
现在,这是页面解析器过滤器(上面的#1):
namespace JG.ParserFilter {
using System;
using System.Collections;
using System.Web.UI;
using System.Web.Mvc;
internal class CustomViewTypeParserFilter : PageParserFilter
{
private string _viewBaseType;
private DirectiveType _directiveType = DirectiveType.Unknown;
private bool _viewTypeControlAdded;
public override void PreprocessDirective(string directiveName, IDictionary attributes) {
base.PreprocessDirective(directiveName, attributes);
string defaultBaseType = null;
// If we recognize the directive, keep track of what it was. If we don't recognize
// the directive then just stop.
switch (directiveName) {
case "page":
_directiveType = DirectiveType.Page;
defaultBaseType = typeof(JG.ParserFilter.CustomViewPage).FullName; // JG: inject custom types here
break;
case "control":
_directiveType = DirectiveType.UserControl;
defaultBaseType = typeof(JG.ParserFilter.CustomViewUserControl).FullName; // JG: inject custom types here
break;
case "master":
_directiveType = DirectiveType.Master;
defaultBaseType = typeof(System.Web.Mvc.ViewMasterPage).FullName;
break;
}
if (_directiveType == DirectiveType.Unknown) {
// If we're processing an unknown directive (e.g. a register directive), stop processing
return;
}
// Look for an inherit attribute
string inherits = (string)attributes["inherits"];
if (!String.IsNullOrEmpty(inherits)) {
// If it doesn't look like a generic type, don't do anything special,
// and let the parser do its normal processing
if (IsGenericTypeString(inherits)) {
// Remove the inherits attribute so the parser doesn't blow up
attributes["inherits"] = defaultBaseType;
// Remember the full type string so we can later give it to the ControlBuilder
_viewBaseType = inherits;
}
}
}
private static bool IsGenericTypeString(string typeName) {
// Detect C# and VB generic syntax
// REVIEW: what about other languages?
return typeName.IndexOfAny(new char[] { '<', '(' }) >= 0;
}
public override void ParseComplete(ControlBuilder rootBuilder) {
base.ParseComplete(rootBuilder);
// If it's our page ControlBuilder, give it the base type string
CustomViewPageControlBuilder pageBuilder = rootBuilder as JG.ParserFilter.CustomViewPageControlBuilder; // JG: inject custom types here
if (pageBuilder != null) {
pageBuilder.PageBaseType = _viewBaseType;
}
CustomViewUserControlControlBuilder userControlBuilder = rootBuilder as JG.ParserFilter.CustomViewUserControlControlBuilder; // JG: inject custom types here
if (userControlBuilder != null) {
userControlBuilder.UserControlBaseType = _viewBaseType;
}
}
public override bool ProcessCodeConstruct(CodeConstructType codeType, string code) {
if (codeType == CodeConstructType.ExpressionSnippet &&
!_viewTypeControlAdded &&
_viewBaseType != null &&
_directiveType == DirectiveType.Master) {
// If we're dealing with a master page that needs to have its base type set, do it here.
// It's done by adding the ViewType control, which has a builder that sets the base type.
// The code currently assumes that the file in question contains a code snippet, since
// that's the item we key off of in order to know when to add the ViewType control.
Hashtable attribs = new Hashtable();
attribs["typename"] = _viewBaseType;
AddControl(typeof(System.Web.Mvc.ViewType), attribs);
_viewTypeControlAdded = true;
}
return base.ProcessCodeConstruct(codeType, code);
}
// Everything else in this class is unrelated to our 'inherits' handling.
// Since PageParserFilter blocks everything by default, we need to unblock it
public override bool AllowCode {
get {
return true;
}
}
public override bool AllowBaseType(Type baseType) {
return true;
}
public override bool AllowControl(Type controlType, ControlBuilder builder) {
return true;
}
public override bool AllowVirtualReference(string referenceVirtualPath, VirtualReferenceType referenceType) {
return true;
}
public override bool AllowServerSideInclude(string includeVirtualPath) {
return true;
}
public override int NumberOfControlsAllowed {
get {
return -1;
}
}
public override int NumberOfDirectDependenciesAllowed {
get {
return -1;
}
}
public override int TotalNumberOfDependenciesAllowed {
get {
return -1;
}
}
private enum DirectiveType {
Unknown,
Page,
UserControl,
Master,
}
}
}
这是页面构建器类(上面的#2):
namespace JG.ParserFilter {
using System.CodeDom;
using System.Web.UI;
internal sealed class CustomViewPageControlBuilder : FileLevelPageControlBuilder {
public string PageBaseType {
get;
set;
}
public override void ProcessGeneratedCode(
CodeCompileUnit codeCompileUnit,
CodeTypeDeclaration baseType,
CodeTypeDeclaration derivedType,
CodeMemberMethod buildMethod,
CodeMemberMethod dataBindingMethod) {
// If we find got a base class string, use it
if (PageBaseType != null) {
derivedType.BaseTypes[0] = new CodeTypeReference(PageBaseType);
}
}
}
}
这里是自定义视图页面类:非泛型基础(上面的#3)和泛型派生类(上面的#4):
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Diagnostics.CodeAnalysis;
using System.Web.Mvc;
namespace JG.ParserFilter
{
[FileLevelControlBuilder(typeof(JG.ParserFilter.CustomViewPageControlBuilder))]
public class CustomViewPage : System.Web.Mvc.ViewPage //, IAttributeAccessor
{
public string MyNewProperty { get; set; }
}
[FileLevelControlBuilder(typeof(JG.ParserFilter.CustomViewPageControlBuilder))]
public class CustomViewPage : CustomViewPage
where TModel : class
{
// code copied from source of ViewPage
private ViewDataDictionary _viewData;
public new AjaxHelper Ajax
{
get;
set;
}
public new HtmlHelper Html
{
get;
set;
}
public new TModel Model
{
get
{
return ViewData.Model;
}
}
[SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public new ViewDataDictionary ViewData
{
get
{
if (_viewData == null)
{
SetViewData(new ViewDataDictionary());
}
return _viewData;
}
set
{
SetViewData(value);
}
}
public override void InitHelpers()
{
base.InitHelpers();
Ajax = new AjaxHelper(ViewContext, this);
Html = new HtmlHelper(ViewContext, this);
}
protected override void SetViewData(ViewDataDictionary viewData)
{
_viewData = new ViewDataDictionary(viewData);
base.SetViewData(_viewData);
}
}
}
以下是用户控件的相应类(上面的#5):
namespace JG.ParserFilter
{
using System.Diagnostics.CodeAnalysis;
using System.Web.Mvc;
using System.Web.UI;
[FileLevelControlBuilder(typeof(JG.ParserFilter.CustomViewUserControlControlBuilder))]
public class CustomViewUserControl : System.Web.Mvc.ViewUserControl
{
public string MyNewProperty { get; set; }
}
public class CustomViewUserControl : CustomViewUserControl where TModel : class
{
private AjaxHelper _ajaxHelper;
private HtmlHelper _htmlHelper;
private ViewDataDictionary _viewData;
public new AjaxHelper Ajax {
get {
if (_ajaxHelper == null) {
_ajaxHelper = new AjaxHelper(ViewContext, this);
}
return _ajaxHelper;
}
}
public new HtmlHelper Html {
get {
if (_htmlHelper == null) {
_htmlHelper = new HtmlHelper(ViewContext, this);
}
return _htmlHelper;
}
}
public new TModel Model {
get {
return ViewData.Model;
}
}
[SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public new ViewDataDictionary ViewData {
get {
EnsureViewData();
return _viewData;
}
set {
SetViewData(value);
}
}
protected override void SetViewData(ViewDataDictionary viewData) {
_viewData = new ViewDataDictionary(viewData);
base.SetViewData(_viewData);
}
}
}
namespace JG.ParserFilter {
using System.CodeDom;
using System.Web.UI;
internal sealed class CustomViewUserControlControlBuilder : FileLevelUserControlBuilder {
internal string UserControlBaseType {
get;
set;
}
public override void ProcessGeneratedCode(
CodeCompileUnit codeCompileUnit,
CodeTypeDeclaration baseType,
CodeTypeDeclaration derivedType,
CodeMemberMethod buildMethod,
CodeMemberMethod dataBindingMethod) {
// If we find got a base class string, use it
if (UserControlBaseType != null) {
derivedType.BaseTypes[0] = new CodeTypeReference(UserControlBaseType);
}
}
}
}
最后,这是一个示例视图,显示了这一点:
<%@ Page Language="C#" MyNewProperty="From @Page directive!" Inherits="JG.ParserFilter.CustomViewPage" %> <%=Model.SomeString %>
this.MyNewPrroperty = <%=MyNewProperty%>
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