C#

[DllImport("wininet.dll", CharSet=CharSet.Auto, SetLastError=true)]
static extern bool InternetGetCookie(string url, string name, [Out] string data,
  ref int size);

public string GetCookie(string url, string name)
{
  int size = 0;
  string data = null;
  // Get the size for 'data' first.
  if (!InternetGetCookie(url, name, null, ref size))
  {
    if (Marshal.GetLastWin32Error() == 122) // ERROR_INSUFFICIENT_BUFFER
    {
      data = new string('\0', size);
      if (InternetGetCookie(url, name, data, ref size))
        return data.Trim();
    }
  }
  return null;
}

public class DragDropTreeView : TreeView
{
  public DragDropTreeView()
  {
    AllowDrop = true;
  }
  // ...
  protected override void OnItemDrag(ItemDragEventArgs e)
  {
    TreeNode node = e.Item as TreeNode;
    if (node != null)
    {
      DataObject data = new DataObject("TreeNode", node);
      DoDragDrop(data, DragDropEffects.Copy);
    }
  }
  protected override void OnDragOver(DragEventArgs e)
  {
    if (e.Data.GetDataPresent("TreeNode") &&
       (e.AllowedEffect & DragDropEffects.Copy) != 0)
      e.Data.Effect = DragDropEffects.Copy;
  }
  protected override void OnDragDrop(DragEventArgs e)
  {
    TreeNode node = e.Data.GetData("TreeNode") as TreeNode;
    if (node != null)
    {
      Point p = PointToClient(new Point(e.X, e.Y));
      TreeNode parent = GetNodeAt(p);
      if (parent != null) parent.Nodes.Add(node);
    }
  }
}