asp.net mvc 3 剃刀视图 ->元组问题的强类型列表 [英] asp.net mvc 3 razor view -> strongly typed List of tuple problem

问题描述

我在使用 asp.net MVC 剃刀视图时遇到了一个奇怪的问题.

I'm having an odd problem with asp.net MVC razor view.

我希望我的模型是一个 List> 这在我的其他 c# 方法中完全有效.但是当我将它粘贴到 @model 声明中时，它似乎只挑选出元组的字符串部分.所以我没有整数.只有 item1.

I want my model to be a List<Tuple<string, int, int, int, int>> which is perfectly valid in my other c# methods. But when I paste it into the @model declaration it seems to only pick out the string part of the tuple. So I have no ints. Only item1.

如果我将它绑定到元组而不是列表，则不会出现此问题.

This problem is not present if I make it bind to a Tuple instead of the List.

好像生成的代码有问题，所以这可能是剃刀视图中的一个错误?

Seems like the generated code is wrong, so perhaps this is a bug in razor view?

我在编译时遇到的错误是:

The error I get at compilation is:

Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. 

Compiler Error Message: CS1003: Syntax error, '>' expected

Source Error:


Line 27:     
Line 28:     
Line 29:     public class _Page_Views_Dashboard_DestinationStatistics_cshtml : System.Web.Mvc.WebViewPage<List<Tuple<string {
Line 30:         
Line 31: #line hidden

为了隔离这个问题，我做了以下事情:

To isolate this problem I did the following thing:

创建一个空的 asp.net mvc 项目.创建一个新视图.粘贴以下代码.

Create an empty asp.net mvc project. Create a new view. Past the following code.

@model List<Tuple<string, int, int, int, int>>

@foreach (var stat in Model)
{
    <tr>
        <td>
            @stat.Item1
        </td>
        <td>
            @stat.Item2
        </td>
        <td>
            @stat.Item3
        </td>
        <td>
            @stat.Item4
        </td>
        <td>
            @stat.Item5
        </td>
    </tr>
}

我知道我可以创建一个类或一个结构来保存数据.只是出于好奇而问

I know I can just create a class or a struct to hold the data instead. Just asking out of curiosity

在此处解决并报告给 MVC 团队 http://aspnet.codeplex.com/workitem/8652

Solved and reported to the MVC team here http://aspnet.codeplex.com/workitem/8652

推荐答案

EDIT 我在这里删减了一些正在进行的评论 - 只需查看历史记录即可.

因此，您可以使用 1、2、3 或 4 元组通用参数进行此操作，但不适用于 5.一旦您使用 5 个参数，它就会生成如下代码:

So you can make this work with 1, 2, 3 or 4 tuple generic parameters but it doesn't work with 5. As soon as you use 5 parameters it generates code like this:

 public class _Page_Views_Home_Index_cshtml : 
   System.Web.Mvc.WebViewPage<List<System.Tuple<string {

我只想知道它是否是字符长度限制，所以我生成了一个这样的类:

I wanted to just find out if it's a character-length limitation, so I generated a class like this:

namespace ASP{  //same namespace that the backend code for the page is generated
  public class T { } 
}

并更改了模型声明:

@model List<Tuple<T,T,T,T,T>>.

最后(见历史)我得到了

In the end (see the history) I got to

@inherits System.Web.Mvc.WebViewPage<Tuple<T,T,T,T,T>>

同样的问题！@model关键字没有问题...

Same problem! It's not a problem with the @model keyword...

花了一些时间(通读 MVC3 和 Razor 源代码，向该解决方案添加了一些测试) - 但这里有一个测试说明了我们为什么会收到此错误:

It took a while (reading through the MVC3 and Razor source, adding a couple of tests to that solution) - but here's a test that shows the why we get this error:

[TestMethod]
public void TestMethod()
{
  System.CodeDom.CodeTypeReferenceCollection c = 
    new CodeDom.CodeTypeReferenceCollection();
  c.Add("Tuple<T,T,T,T>");
  c.Add("Tuple<T,T,T,T,T>");
  //passes
  Assert.AreEqual("Tuple<T,T,T,T>", c[0].BaseType);
  //fails
  Assert.AreEqual("Tuple<T,T,T,T,T>", c[1].BaseType);    
}

所以 - 四参数版本通过，但没有 5 参数版本.

So - the four-parameter version passes, but not the 5 parameter version.

猜猜看 - 实际值是 Tuple - 即截断的泛型类型名称 截断方式与您在代码中观察到的完全相同.

And guess what- the actual value is Tuple<T - i.e. a truncated generic type name truncated exactly the same way that you've observed in your code.

标准 Razor 解析器和 Mvc Razor 解析器在解析 @inherits 或 @model 关键字时都使用 CodeTypeReferenceCollection 类型.下面是代码生成过程中 @inherits 的代码:

Both the standard Razor parser and the Mvc Razor parser use the CodeTypeReferenceCollection type when parsing either the @inherits or @model keyword. Here's the code for @inherits during code generation:

protected internal virtual void VisitSpan(InheritsSpan span) {
  // Set the appropriate base type
  GeneratedClass.BaseTypes.Clear();
  GeneratedClass.BaseTypes.Add(span.BaseClass);

  if (DesignTimeMode) {
    WriteHelperVariable(span.Content, InheritsHelperName);
  }
}

GeneratedClass.BaseTypes 是一个 CodeTypeReferenceCollection - 而 span.BaseClass 是一个字符串.在 ILSpy 中，有问题的方法必须是私有方法 CodeTypeReference.Initialize(string typeName, CodeTypeReferenceOptions options).我现在没有足够的时间来弄清楚它为什么会中断 - 但我认为这是微软开发人员的工作:) 下面更新 - 无法抗拒.我现在知道哪里不对了

GeneratedClass.BaseTypes is a CodeTypeReferenceCollection - and span.BaseClass is a string. Following that through in ILSpy, the offending method must be the private method CodeTypeReference.Initialize(string typeName, CodeTypeReferenceOptions options). I've not enough time now to figure out why it breaks - but then that's a Microsoft developer's job I think :) Update below - couldn't resist. I now know where it's wrong

您不能在 Razor @inherits 或 @model 语句中使用超过 4 个参数的泛型(至少在 C# 中 - 不了解 VB).Razor 解析器似乎错误地使用了 CodeTypeReference 类型.

You can't use generics with more than 4 parameters in either Razor @inherits or @model statements (at least in C# - don't know about VB). It appears that the Razor parser is incorrectly using the CodeTypeReference type.

CodeTypeReference 所做的一件事是通过调用方法 CodeTypeReference.RipOffAssemblyInformationFromTypeName(string typeName) 从传递的类型名称中剥离程序集名称信息.

One of the things that CodeTypeReference does is strip off assembly name information from a passed type name with a call to the method CodeTypeReference.RipOffAssemblyInformationFromTypeName(string typeName).

当然，如果你仔细想想 - Tuple 就像一个程序集限定的类型名称:类型名称 = 元组、Assembly = T、Version=T、Culture=T、PublicKeyToken=T>(如果您编写了一个非常糟糕的 C# 解析器！).

And of course, if you think about it - Tuple<T,T,T,T,T> is just like an assembly-qualified type name: With the type name = Tuple<T, Assembly = T, Version=T, Culture=T, PublicKeyToken=T (if you write a really BAD C# parser!).

果然 - 如果你传入 Tuple 作为类型名称 - 你实际上得到了一个 Tuple.

Sure enough - if you pass in Tuple<T,T,T,T,T,T> as the type name - you actually get a Tuple<T,T>.

深入研究代码，它准备接收一个语言中立的类型名(例如，处理 '[' 但没有处理 '<')，因此，实际上，MVC 团队不应该只处理 C# 类型名直接从我们的源头开始.

Looking deeper into the code, it's primed to receive a language-neutral typename (handles '[' but nothing for '<', for example) so, actually, the MVC team shouldn't just be handing the C# typename from our source straight through.

MVC 团队需要改变他们生成基本类型的方式 - 他们可以使用 public CodeTypeReference(string typeName, params CodeTypeReference[] typeArguments) 新引用的构造函数(而不是仅仅依靠 .Add(span.BaseClass) 创建它)，并解析泛型参数本身，因为它们知道类型名称将是 C#/VB 风格 - 不是语言中立的 .Net 风格，带有括号等作为实际名称的一部分.

The MVC team needs to change how they generate the base type - They could use the public CodeTypeReference(string typeName, params CodeTypeReference[] typeArguments) constructor for a new reference (instead of just relying on the .Add(span.BaseClass) creating it), and parse the generic parameters themselves since they know that the type name will be C#/VB style - not language-neutral .Net style with brackets etc as part of the actual name.

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