SPAttachmentCollection class

Use the Attachments property of the SPListItem class to return the collection of attachments for a list item. To create an attachment, use the Add method

Use an indexer to return the file name of a single attachment from the collection. For example, assuming the collection is assigned to a variable named collAttachments , use collAttachments[index] in C#, or collAttachments(index) in Visual Basic, where index is the index number of the attachment in the collection.

The following code example shows how to attach all the files from a Shared Documents document library to the first list item within a list that appears on every subsite under the site.

The Add method of the SPAttachmentCollection class requires that you pass the file as a parameter in binary format. Therefore, the example uses the OpenBinary method of the SPFile class to open each file within the folder in binary format.

Note
Certain objects implement the IDisposable interface, and you must avoid retaining these objects in memory after they are no longer needed. For information about good coding practices, see Disposing Objects.

Reference