如何在 ASP.NET MVC 中定义视图级变量？

Question

我有一个 cshtml 部分视图（Razor 引擎），用于递归渲染某些内容。我在此视图中定义了两个声明性 HTML 帮助器函数，我需要在它们之间共享一个变量。换句话说，我想要一个视图级变量（而不是函数级变量）。

@using Backend.Models;
@* These variables should be shared among functions below *@    
@{
    List<Category> categories = new ThoughtResultsEntities().Categories.ToList();
    int level = 1;
}

@RenderCategoriesDropDown()

@* This is the first declarative HTML helper *@
@helper RenderCategoriesDropDown()
{
    List<Category> rootCategories = categories.Where(c => c.ParentId == null).ToList();
    <select id='parentCategoryId' name='parentCategoryId'>
    @foreach (Category rootCategory in rootCategories)
    {
        <option value='@rootCategory.Id' class='level-@level'>@rootCategory.Title</option>
        @RenderChildCategories(rootCategory.Id);
    }
</select>
}

@* This is the second declarative HTML helper *@
@helper RenderChildCategories(int parentCategoryId)
{
    List<Category> childCategories = categories.Where(c => c.ParentId == parentCategoryId).ToList();
    @foreach (Category childCategory in childCategories)
    {
        <option value='@childCategory.Id' class='level-@level'>@childCategory.Title</option>
        @RenderChildCategories(childCategory.Id);
    }
}

Answer 1

你不能这样做。您需要将它们作为参数传递给辅助函数：

@using Backend.Models;
@{
    List<Category> categories = new ThoughtResultsEntities().Categories.ToList();
    int level = 1;
}

@RenderCategoriesDropDown(categories, level)

@helper RenderCategoriesDropDown(List<Category> categories, int level)
{
    List<Category> rootCategories = categories.Where(c => c.ParentId == null).ToList();
    <select id='parentCategoryId' name='parentCategoryId'>
    @foreach (Category rootCategory in rootCategories)
    {
        <option value='@rootCategory.Id' class='level-@level'>@rootCategory.Title</option>
        @RenderChildCategories(categories, level, rootCategory.Id);
    }
    </select>
}

@helper RenderChildCategories(List<Category> categories, int level, int parentCategoryId)
{
    List<Category> childCategories = categories.Where(c => c.ParentId == parentCategoryId).ToList();
    @foreach (Category childCategory in childCategories)
    {
        <option value='@childCategory.Id' class='level-@level'>@childCategory.Title</option>
        @RenderChildCategories(categories, level, childCategory.Id);
    }
}

Answer 2

你可以这样做。 View只是一个类。您可以轻松地在此类上声明一个新字段，并在视图代码中的任何位置使用它：

@functions
{
    private int level = 0;
}