如何为列表创建索引访问器 <T> 我在自定义课程中拥有的物业？

Question

Here's the example:

    /// <summary>
    /// Collection of SednaTreeViewItems used to populate the SednaTreeView.
    /// </summary>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public List<SednaTreeViewItem> TreeNodes
    {
        get { return treeNodes; }
        set 
        {
            ultraTree.Nodes.Clear();
            treeNodes = value;
            foreach (var item in treeNodes)
            {
                UltraTreeNode node = new UltraTreeNode(item.ValueMember, item.DisplayMember);
                ultraTree.Nodes.Add(node);
            }

            if (treeNodes.Count() > 0)
                ultraTree.ActiveNode = ultraTree.Nodes[0];
        }
    }

    /// <summary>
    /// SednaTreeViewItem that is currently selected in the SednaTreeView.
    /// </summary>
    public SednaTreeViewItem SelectedItem
    {
        get 
        {
            if (ultraTree.SelectedNodes != null)
            {
                var node = ultraTree.SelectedNodes[0];
                SednaTreeViewItem item = new SednaTreeViewItem(node.Key, node.Text);
                return item;
            }
            else
                return null;                
        }

        set 
        {
            ultraTree.ActiveNode = ultraTree.Nodes[value.ValueMember];
        }
    }

I'd like to use my control in this way. For example, someone wants to set the selected tree view node during runtime, I'd like something like:

treeViewInvestors.SelectedItem = treeViewInvestor.TreeNodes[userIdKey];

Where userIdKey is a unique key that's already in place behind the scenes.

Basically, is there a way to create an index "[]" accessor for my property?

Answer 1

Implement indexer property like:

public SednaTreeViewItem this[int index]//or public T this[int index]
{
   get { return ultraTree[index]; }
   set { ultraTree[index] = value; }
}

Answer 2

If the exposed node collection property is a List (that already has an indexer of type int), and you need an indexer of another type, then you could expose the treenode collection as a subclass of list that has the other type of indexer:

public class NodeList : List<Node>
{
   public TNode this[Key key] 
   {
       get { return nodes.Where(n => n.Key == key).SingleOrDefault(); }
   }
}

Then you can access by both kinds of index

var nodeByKey = treeViewInvestor.TreeNodes[key];
var nodeByIndex = treeViewInvestor.TreeNodes[index].