C # implement the drag function in the winform Treeview Control (1)

Using system;
Using system. Collections. Generic;
Using system. componentmodel;
Using system. Data;
Using system. drawing;
Using system. text;
Using system. Windows. forms;

Namespace treeviewtest
{
Public partial class form1: Form
{
Public form1 ()
{
Initializecomponent ();
}

Private void form1_load (Object sender, eventargs E)
{
Treenode node;
Int X, Y;
For (x = 0; x <= 3; X ++)
{
Node = tvwtest. nodes. Add (string. Format ("root node {0}", x * 4 ));
For (y = 1; y <= 4; y ++)
{
Node = node. nodes. Add (string. Format ("-node", x * 4 + y ));
}
}
}

Private void tvwtest_itemdrag (Object sender, itemdrageventargs E)
{
If (E. Button = system. Windows. Forms. mousebuttons. Left)
{
Dodragdrop (E. Item, dragdropeffects. Move );
}
Else if (E. Button = system. Windows. Forms. mousebuttons. Right)
{
Dodragdrop (E. Item, dragdropeffects. copy );
}
}

Private void tvwtest_dragenter (Object sender, drageventargs E)
{
E. effect = E. allowedeffect;
}

Private void tvwtest_dragover (Object sender, drageventargs E)
{
Point targetpoint = (Treeview) (sender). pointtoclient (new point (E. X, E. y ));
(Treeview) (sender). selectednode = (Treeview) (sender). getnodeat (targetpoint );
}

Private void tvwtest_dragdrop (Object sender, drageventargs E)
{
Point targetpoint = (Treeview) (sender). pointtoclient (new point (E. X, E. y ));
Treenode targetnode = (Treeview) (sender). getnodeat (targetpoint );
Treenode draggednode = (treenode) (E. Data. getdata (typeof (treenode )));
If (! Draggednode. Equals (targetnode )&&! Containsnode (draggednode, targetnode ))
{
If (E. effect = dragdropeffects. Move)
{
Draggednode. Remove ();
Targetnode. nodes. Add (draggednode );

}
Else if (E. effect = dragdropeffects. copy)
{
Targetnode. nodes. Add (treenode) (draggednode. Clone ()));
}
Targetnode. Expand ();
}

}
Private bool containsnode (treenode nodel, treenode node2)
{
If (node2.parent = NULL)
{
Return false;
}
If (node2.parent. Equals (nodel ))
{
Return true;
}
Return containsnode (nodel, node2.parent );
}

}
}