LINQ. Insert. How can I do this?

[shapper]

Hello,

I have 3 tables:

Files FileID, Url, ...
Tags TagID, Name, ...
FilesTags FileID, TagID, ...

FilesTags is used to associate tags to each file.

Before I update a file I have the following data:
1. File Data
2. List of File Tags (TagsList)

I need to:
1. Update File Data (This is done)
2. Update File Tags ...

I am having problems updating the file tags using LINQ.

The sequence I am trying to create is:

FOR each Tag in TagsList {

Exists = Find Tag in Tags table given its name

IF Not Exists Create Tag in Tags table using the Name

Use found or created Tag ID and add record to FilesTags with
FileID and TagID
END

How can I translate this to LINQ?

Thanks,
Miguel