Question

I have a loop that is looping through a document library like in the example below.

foreach (SPListItem item in DocumentLibrary)
{
}

How do I tell if the SPListItem is a document or a folder?

Answer 1

The Folder property of the list item will be null if the item is not a folder, so you can write:

public bool IsFolder(SPListItem item)
{
    return item.Folder != null;
}

In the same way, the File property of the item will be null if the item is not a document. However, the documentation advises against using this property in that case:

The File property also returns null if
the item is a folder, or if the item
is not located in a document library,
although it is not recommended that
you call this property in these cases.

An alternate way is to check the BaseType property of the list:

public bool IsDocument(SPListItem item)
{
    return !IsFolder(item)
        && item.ParentList.BaseType == SPBaseType.DocumentLibrary;
}