How to fetch folders and subfolders from sharepoint document library

Question

 I have document library with name . Under "Documents" there are some folders.Under some folders there are some subfolders.
I need to fetch the folders in to dropdown list. IF I select some folder in dropdownlist,I need to fetch subfolders of that folder to some other dropdownlist.
How to acheive this

Answer 1

The below function get the folder name and id of subfolder where items stored folder = item.folder.  Initially it will be null.
static
string GetParentFolder(SPListItem itemToFind,
SPFolder folder) 
SPQuery query =
new SPQuery();
query.Query = "<Where><Eq><FieldRef Name=\"ID\"/><Value Type=\"Integer\">"+ itemToFind.ID +"</Value></Eq></Where>";
query.Folder = folder;
query.ViewAttributes = "Scope=\"Recursive\"";
SPListItemCollection items = itemToFind.ParentList.GetItems(query);
int intpartentFolderID=0 ;
if (items.Count > 0)
foreach (SPListItem item
in items)
SPFile f = item.Web.GetFile(item.Url);
string test11 = f.ParentFolder.Name;
intpartentFolderID = f.ParentFolder.Item.ID;
return (intpartentFolderID.ToString());
         return (intpartentFolderID.ToString());