在razor中使用递归，巧用递归

原文发布时间为：2011-04-20 —— 来源于本人的百度文章 [由搬家工具导入]

Learning Razor–Writing an Inline Recursive HTML Helper

Writing an Inline Recursive Html Helper

The Spark view engine provides you with the ability to define inline macros that allow for recursive calls (Read Louis DeJardin blog on the topic here, and additional documentation here).  These macros are extremely useful for rendering a hierarchical structure such as the one in the following snippet.

<ul>
  <li>Fuller, Andrew
    <ul>
      <li>Davolio, Nancy</li>
      <li>Leverling, Janet</li>
      <li>Peacock, Margaret</li>
      <li>Buchanan, Steven
        <ul>
          <li>Suyama, Michael</li>
          <li>King, Robert</li>
          <li>Dodsworth, Anne</li>
        </ul>
      </li>
      <li>Callahan, Laura</li>
    </ul>
  </li>
</ul>

Now, the Razor view engine allows you to easily build a hierarchical structure by the use of inline HTML helpers that can be called recursively.  The following is a basic snippet of a “Hello World” inline HTML helper, and a call to trigger its functionality.

@HelloWorld("Roberto!")

@helper HelloWorld(string name) {
    <h1>Hello World! @name</h1>
}

Finally, if we wanted to output the html from the first snippet using Razor we could write the following inline HTML helper.

@model IEnumerable<OrganizationNodeViewModel>
@using MVC3.Playground.ViewModels;
@{
    View.Title = "OrganizationTree";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>OrganizationTree</h2>

@OrgTree(Model, null);

@helper OrgTree(IEnumerable<OrganizationNodeViewModel> nodes, int? parentId) {
    if (nodes.Any(n => n.ParentId == parentId)) {
    <ul>
        @foreach (var node in nodes.Where(n => n.ParentId == parentId)) {
            <li>
                @node.DisplayName
                @OrgTree(nodes, node.Id)
            </li>
        }
    </ul>
    }
}