访问自定义属性在T4模板（VS2012 MVC4） [英] Accessing Custom Attributes in a T4 Template (VS2012 MVC4)

问题描述

我想访问我的自定义属性，如 SortableAttribute 附着在T4控制器模板，我写我的模型属性。我复制了List.tt类块，组件和进口的样板。

I'm trying to access my custom attributes like SortableAttribute attached to my model properties in a T4 Controller template I'm writing. I've copied the class block, assemblies and imports from List.tt as boilerplate.

首先，我想投的属性如下：

First I tried to cast the attributes as follows:

<#+
string SortableBy(PropertyInfo property)
{
    foreach (object attribute in property.GetCustomAttributes(true))
    {
        var sortable = attribute as SortableAttribute;
        if (sortable != null) return sortable.By == "" ? property.Name : sortable.By;
    }
    return property.Name;
}
#>

不过，这没有产生任何积极的结果，因为我的项目的命名空间是未知的T4。要解决这个问题，我已经加了我的项目的DLL和进口所需的命名空间。

This however yielded no positive results since my project's namespace is unknown to T4. To resolve this, I have added my project's dll and imported the required namespace.

<#@ assembly name ="c:\path\to\MyProject\bin\MyProject.dll" #>
<#@ import namespace= "MyProject.Filters" #>

这似乎是成功的第一（例如没有在命名空间导入错误），但它依然没有找到我的属性。如果我换成 SortableAttribute 与 MyProject.Filters.SortableAttribute ，该错误信息是， SortableAttribute 未在 MyProject.Filters 找到。

It seemed to be successful at first (eg. no errors on the namespace import), but it still did not find my attributes. If I replaced SortableAttribute with MyProject.Filters.SortableAttribute, the error message was that SortableAttribute was not found in MyProject.Filters.

要解决这个问题，我已经改变了我的code如下：

To overcome this, I've changed my code as follows:

<#+
string SortableBy(PropertyInfo property)
{
    foreach (object attribute in property.GetCustomAttributes(true))
    {
        if (attribute != null && attribute.GetType().Name == "SortableAttribute")
        {
            var sortableBy = (string) attribute.GetType().GetProperty("By").GetValue(attribute, null);
            return sortableBy == "" ? property.Name : sortableBy;
        }
    }
    return property.Name;
}
#>

我想我已经中奖，但我很快就意识到， property.GetCustomAttributes（真）将返回所有属性，但不是我的......

I thought I've hit the jackpot, but I soon had to realise that property.GetCustomAttributes(true) returns all attributes but not mine...

一个例子模型：

public class MyModel
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [Required]
    [Display(Name = "Full Name")]
    [Sortable]
    public int Name { get; set; }
}

实施 SortableAttribute ：

using System;

namespace MyProject.Filters
{
    [AttributeUsage(AttributeTargets.Property)]
    public class SortableAttribute : Attribute
    {
        public SortableAttribute(string by = "")
        {
            this.By = by;
        }

        public string By { get; private set; }
    }
}

您可以请点我正确的方向？

Can you please point me to the right direction?

任何帮助是极大AP preciated！

Any help is greatly appreciated!

编辑：

原来， property.GetCustomAttributes（真）不会返回我的属性，但是在SortableBy下面前pression始终计算为空：

It turns out that property.GetCustomAttributes(true) does return my attributes, but the following expression in SortableBy always evaluates to null:

(string) attribute.GetType().GetProperty("By").GetValue(attribute, null);

知道为什么这可以吗？

Any idea why this can be?

推荐答案

记住：建立修复了很多问题，但 REBUILD 可以解决这一切。

Remember: Build fixes a lot of problems, but REBUILD can fix it all!

要回顾一下，并帮助别人写T4模板，这里有一些工作code，它可以作为样板：

To recap and to help others writing T4 templates, here are some working code that can be used as boilerplate:

在.TT文件中读取自定义属性（基于脚手架（）中的所有默认视图模板）：

Reading custom attribute in a .tt file (based on Scaffold() in any default view template):

<#+
string SortableBy(PropertyInfo property)
{
    foreach (object attribute in property.GetCustomAttributes(true))
    {
        var sortable = attribute as SortableAttribute;
        if (sortable != null) return sortable.By == "" ? property.Name : sortable.By;
    }
    return property.Name;
}
#>

型号：

public class MyModel
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    [Required]
    [Display(Name = "Full Name")]
    [Sortable]
    public int Name { get; set; }
}

实施 SortableAttribute ：

using System;

namespace MyProject.Filters
{
    [AttributeUsage(AttributeTargets.Property)]
    public class SortableAttribute : Attribute
    {
        public SortableAttribute(string by = "")
        {
            this.By = by;
        }

        public string By { get; private set; }
    }
}

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