| Melon00 2006-06-06, 10:53 am |
| I have a class I am calling SimTreeNode which is a System.Windows.Forms.TreeNode type. I am planning on using this class within my TreeView class.
Class Definition:
code:
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
namespace SimTree
{
public class SimTreeNode : System.Windows.Forms.TreeNode
{
//public static explicit operator SimTreeNode(TreeNode tn)
//{
//}
}
}
As you can see, I don't do anything more or less than the TreeNode class.
The problem is, when I try to use my SimTreeNode in place of any TreeNode in my TreeView class, it throws runtime errors.
Here is the snippet of code I am doing the conversion.
code:
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Text;
using System.Windows.Forms;
using System.Xml;
using System.Xml.Serialization;
using SimTree.Properties;
using System.Runtime.InteropServices;
namespace SimTree
{
public partial class SimTree : System.Windows.Forms.TreeView
{
private void SimTree_ItemDrag(object sender, ItemDragEventArgs e)
{
// Do not allow anything other than devices to be dragged
Point pt = this.PointToClient(Control.MousePosition);
SimTreeNode tn = (SimTreeNode)this.GetNodeAt(pt); // <--- Runtime error here
...
}
}
}
Runtime Error:
code:
Unable to cast object of type 'System.Windows.Forms.TreeNode' to type 'SimTree.SimTreeNode'.
I would like to know why I cant caste my derived type to my base type.
According to a million online forums, I don't need to make an explicit operator to caste to/from base types. I actually tried to make an explicit caste operator if you look at my comments in the SimTree.SimTreeNode class, but gave me a compiler error:
code:
Error 1 'SimTree.SimTreeNode.explicit operator SimTree.SimTreeNode(System.Windows.Forms.TreeNode)': user-defined conversion to/from base class C:\...\SimTree\SimTreeNode.cs 10 23 SimTree
This really doesn't make any sense to me as the compiler SHOULDN'T have anyway of telling how to convert a base type to a derived type without me telling it explicitly.
I am hitting brick walls left and right with this simple thing I want to do. |