[英]Implementing IEnumerable on a tree structure
Based on the work of these guys:基于这些人的工作:
I am trying to implement a TreeView helper that would be used as such:我正在尝试实现一个 TreeView 助手,它可以这样使用:
<%= Html.TreeView("records",
Library.Instance.Records,
r => r.Children,
r => r.ID) %>
And the tree structure is defined like this:树结构定义如下:
public class Tree<T> : TreeNode<T> where T : TreeNode<T>
{ }
public class TreeNode<T> : IDisposable where T : TreeNode<T>
{
public T Parent { get; set; }
public TreeNodeList<T> Children { get; set; }
}
public class TreeNodeList<T> : List<TreeNode<T>> where T : TreeNode<T>
{
public T Parent;
public T Add(T node)
{
base.Add(node);
node.Parent = (T)Parent;
return node;
}
public void Remove(T node)
{
if (node != null)
node.Parent = null;
base.Remove(node);
}
}
And the TreeView helper has this signature: TreeView 助手具有以下签名:
public static string TreeView<T>(this HtmlHelper htmlHelper, string treeId,
IEnumerable<T> rootItems, Func<T, IEnumerable<T>> childrenProperty,
Func<T, string> itemContent, bool includeJavascript, string emptyContent)
{
...
}
So as a result i need my Tree struture to implement IEnumerable so i can use it with the TreeView helper, and this leads to the question: where and how would i implement IEnumerable in this situation?因此,我需要我的 Tree 结构来实现 IEnumerable,以便我可以将它与 TreeView 助手一起使用,这导致了一个问题:在这种情况下,我将在哪里以及如何实现 IEnumerable?
This article by Wes Dyer is good reading for anyone who wants to implement a recursive tree iterator: Wes Dyer 的这篇文章适合任何想要实现递归树迭代器的人阅读:
https://docs.microsoft.com/en-us/archive/blogs/wesdyer/all-about-iterators https://docs.microsoft.com/en-us/archive/blogs/wesdyer/all-about-iterators
I don't fully understand the exact details of your tree structure, but here is a simple implementation that takes a generic tree of nodes and recursively renders it into html lists.我不完全了解您的树结构的确切细节,但这里有一个简单的实现,它采用节点的通用树并递归地将其呈现为 html 列表。
public static string TreeView<T>(IEnumerable<T> rootItems,
Func<T, IEnumerable<T>> childrenProperty,
Func<T, string> itemContent)
{
if (rootItems == null || !rootItems.Any()) return null;
var builder = new StringBuilder();
builder.AppendLine("<ul>");
foreach (var item in rootItems)
{
builder.Append(" <li>").Append(itemContent(item)).AppendLine("</li>");
var childContent = htmlHelper.TreeView(treeId,
childrenProperty(item),
childrenProperty,
itemContent);
if (childContent != null)
{
var indented = childContent.Replace(Environment.NewLine,
Environment.NewLine + " ");
builder.Append(" ").AppendLine(indented);
}
}
builder.Append("</ul>");
return builder.ToString();
}
The node class that I'm using is relatively simple with only two properties.我使用的节点类相对简单,只有两个属性。
public class Node<T>
{
public Node(T data)
{
Data = data;
Children = new List<Node<T>>();
}
public T Data { get; private set; }
public ICollection<Node<T>> Children { get; private set; }
}
Here is some test code that outputs the tree to the console.这是一些将树输出到控制台的测试代码。
var Records = new[] {
new Node<string>("one") {
Children = {
new Node<string>("one-one") {
Children = {
new Node<string>("one-one-one"),
new Node<string>("one-one-two"),
new Node<string>("one-one-three")
}
},
new Node<string>("one-two"),
new Node<string>("one-three")
}
},
new Node<string>("two"),
new Node<string>("three")
};
Console.WriteLine(TreeView(Records,
r => r.Children,
r => r.Data));
And here are the results from the above code.以下是上述代码的结果。
<ul>
<li>one</li>
<ul>
<li>one-one</li>
<ul>
<li>one-one-one</li>
<li>one-one-two</li>
<li>one-one-three</li>
</ul>
<li>one-two</li>
<li>one-three</li>
</ul>
<li>two</li>
<li>three</li>
</ul>
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