使用Func创建递归方法助手. [英] Creating recursive method helper with Func<>

问题描述

我有两个带有这些签名的方法助手:

I have two method helper with theses signatures:

@helper CreateNavigation(int parentId，int depthNavigation)

@helper CreateNavigation(int parentId, int depthNavigation)

@helper导航(int parentId，int depthNavigation)

@helper Navigation(int parentId, int depthNavigation)

我试图将其转换为在ASP.NET Core 2中使用的正确方法.

I have tried to convert it to a proper method for using in ASP.NET Core 2.

但是我在VS2017 IDE中遇到了一个错误:

But I got an error in VS2017 IDE that is:

1-使用未分配的局部变量"Navigation"
2-局部变量 访问前可能未初始化导航"

1- Use of unassigned local variable 'Navigation'
2- local variable 'Navigation' might not be initialized before accessing

我该如何解决?

@using Microsoft.AspNetCore.Html
@using Microsoft.AspNetCore.Mvc.Razor
@model List<Jahan.Beta.Web.App.Models.Comment>

@{
    Func<int, int, int, HelperResult> CreateNavigation
        = (parentId, depthNavigation) => new Func<object, HelperResult>(
    @<text>@{
                Comment parent = Model.SingleOrDefault(r => r.Id == parentId);
                depthNavigation = 6;
        @Navigation(parentId, depthNavigation)
    }</text>)(null);
}
@{

    Func<int, int, HelperResult> Navigation
        = (parentId, depthNavigation) => new Func<object, HelperResult>(
    @<text>@{
                var parent = Model.Children(parentId);
                if (//condition)
                {
                    if (//condition)
                    {
                        foreach (var comment in Model)
                        {
                            if (//condition)
                            {
                                <li><p>@comment.Description</p></li>
                                @Navigation(comment.Id, depthNavigation)
                            }
                        }
                    }
                }
    }</text>)(null);
}

推荐答案

我遇到了同样的问题，我能够通过先声明委托并将其设置为null，然后添加如下实现来解决此问题:

I had the same problem and I was able to solve it by declaring the delegate first and setting it to null, then adding the implementation like this:

@{Func<IEnumerable<Foo>, IHtmlContent> DisplayTree = null;}
@{DisplayTree = @<text>@{
  var foos = item;
  <ul>
  @foreach (var foo in foos)
  {
  <li>
    @foo.Title
    @if (foo.Children.Any())
    {
      @DisplayTree(foo.Children)
    }
  </li>
  }
  </ul>
}</text>;}


@DisplayTree(new List<Foo>{...})

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