asp.net mvc 3 剃刀视图 ->元组问题的强类型列表

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<tuple></tuple 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<t - 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.</t

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);
  }
}