C# How to inherit from the treenode class?

Question

I have a class that inherits from TreeNode, called ExtendedTreeNode. To add an object of this type to the treeview is not a problem. But how do I retrieve the object from the treeview?

I have tried this:

TreeNode node = tvManual.Find("path/to/node"); // tvManual is a treeview

return ((ExtendedTreeNode)node).Property;

But this doesn't work. I get this error: Unable to cast object of type 'System.Web.UI.WebControls.TreeNode' to type 'PCK_Web_new.Classes.ExtendedTreeNode'.

What do I have to do to make this work?

------------ SOLUTION -----------------

[Edit] My custom TreeNode class looks like this:

public class ExtendedTreeNode : TreeNode
{
    private int _UniqueId;

    public int UniqueId
    {
        set { _UniqueId = value; }
        get { return _UniqueId; }
    }
    public ExtendedTreeNode()
    {
    }
}

And this way I add Nodes to my treeview:

ExtendedTreeNode TN2 = new ExtendedTreeNode();

TN2.Text = "<span class='Node'>" + doc.Title + "</span>";
TN2.Value = doc.ID.ToString();
TN2.NavigateUrl = "ViewDocument.aspx?id=" + doc.ID + "&doc=general&p=" + parent;
TN2.ImageUrl = "Graphics/algDoc.png";
TN2.ToolTip = doc.Title;
TN2.UniqueId = counter;

tvManual.FindNode(parent).ChildNodes.Add(TN2);

And this way I retrieve my ExtendedTreeNode object:

TreeNode node = tvManual.Find("path/to/node");
ExtendedTreeNode extNode = node as ExtendedTreeNode;
return extNode.UniqueId;

I am using .NET 3.5 SP1

Answer 1

You could try the following to get all nodes under your parent:

TreeNode[] parentNode = treeView1.Nodes.Find (parentid, true);
foreach(TreeNode node in parentNode)
{
    ExtendedTreeNode ext_tree_node = node as ExtendedTreeNode;
    if(ext_tree_node != null)
    {
        // Do your work
    }
}

Answer 2

I assume you're creating the nodes as ExtendedTreeNodes.

I've noticed that the XxxView (ListView, TreeView, DataGridView) controls tend to clone things unexpectedly. Have you implemented ICloneable.Clone ()?

That may work; TreeNode implements Clone () virtually.

I find it easier, though to implement extended properties using the Tag property of the treenode:

TreeNode node = tvManual.Find("path/to/node");
return node.Tag as ExtendedTreeNode;

---

I strongly recommend against using Clone (); it's a fragile pattern. Use the Tag property:

class ExtendedInfo
{
    string NavigateUrl;
    string ImageUrl;
    int UniqueId;

    // other custom properties go here
}

// ...

void CreateTreeNode ()
{
    TreeNode TN = new TreeNode();

    string parent = "parent";    

    TN.Text = "<span class='Node'>" + doc.Title + "</span>";
    TN.Value = doc.ID.ToString();
    TN.ToolTip = doc.Title;

    ExtendedInfo extInfo = new ExtendedInfo;
    extInfo.NavigateUrl = "ViewDocument.aspx?id=" + doc.ID + "&doc=general&p=" + parent;
    extInfo.ImageUrl = "Graphics/algDoc.png";
    extInfo.UniqueId = counter;

    TN.Tag = extInfo;
}

// ...

ExtendedInfo GetExtendedInfo (TreeNode node)
{
    return node.Tag as ExtendedInfo;
}