无法将类型为System.Web.UI.WebControls.TreeNode的对象强制转换为“自定义"节点 [英] Unable to cast an object of type System.Web.UI.WebControls.TreeNode to Custom node

问题描述

我有一个自定义类"Node"，它继承了System.Web.UI.WebControls.TreeNode类.在树视图的SelectedNodeChanged事件上，我试图将Treeview.SelectedNode的类型更改为自定义类型Node.在执行此类型转换时，我收到了InvalidCastException.

********************编辑**********************
SelectedNodeChanged事件HANDLER的定义如下

Hi,

I have a custom class ''Node'' inheriting the System.Web.UI.WebControls.TreeNode class. On the SelectedNodeChanged event of the treeview, I am trying to change the type of Treeview.SelectedNode to the custom type, Node. While performing this type casting I am getting the InvalidCastException.

********************EDIT**********************
The SelectedNodeChanged event HANDLER is defined as follows

protected void tvTreeview_SelectedNodeChanged(object sender, EventArgs e)<br />
{<br />
   TreeNode tn = tvTreeview.SelectedNode;<br />
   Node selectednode = (Node)tn;          //Exception thrown at this line<br />
}<br />

**************************************************

由于"e"的类型为EventArgs，因此没有为其定义任何属性.

有人可以帮我解决这个问题吗?

紧急！

**********************************************

Since ''e'' is of type EventArgs, there are no properties defined for it.

Can anybody please help me with this problem?

Its urgent!!

推荐答案

您可能需要将sender强制转换为适当的类型.

编辑==================

您仍然必须强制发送者来获取选定的节点:

You probably need to cast the sender to the appropriate type instead.

EDIT ==================

You still have to cast the sender to get the selected node:

Treeview tree = sender as TreeView;
Node node = tree.SelectedNode as Node;

没办法！您不能将对TreeNode对象的引用类型转换为Node对象.您只能强制转换引用Node对象的TreeNode引用.例如:

No Way! You cant typecast a reference to a TreeNode object to a Node object. You can only typecast a TreeNode reference that refers to a Node object. For Example:

TreeNode tn = new Node();
Node n = (Node) tn;

因此，请确保tn引用Node对象.

问候.

So make sure that tn refers to a Node object.

Regards.

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