SharePoint - Client Object Model - Get Sub Folder Items - sharepoint-2010

Question

each 'listItem' contains items , how to get them? I'm trying for a while but only fail ,
help , thanks
the camlQuery is from some tests and examples from the web , didn't help ( had many changes)
ClientContext clientContext = new ClientContext("http://xxx.xxx.com");
List list = clientContext.Web.Lists.GetById(new Guid("{F91A0F26-2826-4B3B-AF30-ED7DE4494C7B}"));
clientContext.Load(list);
clientContext.ExecuteQuery();
CamlQuery camlQuery = new CamlQuery();
camlQuery.ViewXml = #"<queryOptions><QueryOptions><ViewAttributes Scope='RecursiveAll'/><Folder></Folder></QueryOptions></queryOptions>";
ListItemCollection listItems = list.GetItems(camlQuery);
clientContext.Load(listItems);
clientContext.ExecuteQuery();
foreach (ListItem listItem in listItems)
{
each lisItem has children/items , how to get them?!
}

Answer 1

I have found the answer , thanks for the helpers... :)
Items is my object I created.
to get "folderServerRelativeUrl" value, you can get it from
(string)listItem ["FileRef"] when you go over the folders from above foreach
public Items GetFolderItems(string folderServerRelativeUrl, List list, ClientContext clientContext)
{
try
{
var result = new Items(); <-- my class
var query = new CamlQuery();
query.FolderServerRelativeUrl = folderServerRelativeUrl;
query.ViewXml = "<View Scope=\"RecursiveAll\"> " +
"<Query>" +
"<Where>" +
"<Eq>" +
"<FieldRef Name=\"FileDirRef\" />" +
"<Value Type=\"Text\">" + folderServerRelativeUrl + "</Value>" +
"</Eq>" +
"</Where>" +
"</Query>" +
"</View>";
var folderItems = list.GetItems(query);
clientContext.Load(folderItems);
clientContext.ExecuteQuery();
foreach (ListItem item in folderItems)
{
// item[ "..." ];
}
return result;
}
catch (Exception)
{
return null;
}
}

Answer 2

Another way to get all items of list folders:
camlQuery.ViewXml = #"<View Scope='RecursiveAll'>
<Query>
<Where>
<Eq>
<FieldRef Name='FSObjType' />
<Value Type='int'>0</Value>
</Eq>
</Where>
</Query>
</View>";

Answer 3

Thank you for this great answer. Just to let you know that the folderServerRelativeUrl variable should be from the root Url (except the http://server). I did have a list named "Vendors" inside documentcenter. That is, siteUrl is http://server/documentcenter and the list name is Vendors. I had to pass "/documentcenter/Vendors/..." as my folderServerRelativeUrl. But that is OK. I am still grateful to you.
Stack Overflow folks, it is so sad that I could not add a comment underneath his answer. I had to submit this comment as an answer. Help me if this could be done in a different way. I do not want to edit his answer.
~Sharmin