[英]Implementing IEnumerable on a tree structure
基於這些人的工作:
我正在嘗試實現一個 TreeView 助手,它可以這樣使用:
<%= Html.TreeView("records",
Library.Instance.Records,
r => r.Children,
r => r.ID) %>
樹結構定義如下:
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);
}
}
TreeView 助手具有以下簽名:
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)
{
...
}
因此,我需要我的 Tree 結構來實現 IEnumerable,以便我可以將它與 TreeView 助手一起使用,這導致了一個問題:在這種情況下,我將在哪里以及如何實現 IEnumerable?
Wes Dyer 的這篇文章適合任何想要實現遞歸樹迭代器的人閱讀:
https://docs.microsoft.com/en-us/archive/blogs/wesdyer/all-about-iterators
我不完全了解您的樹結構的確切細節,但這里有一個簡單的實現,它采用節點的通用樹並遞歸地將其呈現為 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();
}
我使用的節點類相對簡單,只有兩個屬性。
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; }
}
這是一些將樹輸出到控制台的測試代碼。
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));
以下是上述代碼的結果。
<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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