Entity framework query - save/update/delete

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VB

entity-framework

Hi I have my code I have written below and i'm not sure it is correct.
I'm passing a record key form my SQL database to delete record(s) and update record(s).
Do I need to put 'db.SaveChanges()' in more often?
Any pointers would be greatfully recieved. I'm new to EF.
Many Thanks.

What I have tried:

Dim db As New iconportalEntities

'Get records in the Artwork Batch
Dim LogRecords = db.ArtworkRequestLog.Where(Function(c) c.F1Int = ukey)

For Each ArtworkRequestLog In LogRecords

    Dim DataLineUK As Integer = ArtworkRequestLog.ItemKey

    'For each line in Artwork Batch: Update related Data line
    Dim DataRecord = db.Datas.SingleOrDefault(Function(c) c.UK = DataLineUK)
    DataRecord.TemplateName = Nothing
    DataRecord.ArtworkRef = ""
    DataRecord.Grade = Nothing

    'Remove Line from Artwork Batch
    Dim ALogRecord = db.ArtworkRequestLog.SingleOrDefault(Function(c) c.UKEY = ukey)
    db.ArtworkRequestLog.Remove(ALogRecord)

Next


'Now Delete the Artwork Request Batch

Dim ABatchRecord = db.ArtworkBatchRequestLog.SingleOrDefault(Function(c) c.UKEY = ukey)
db.ArtworkBatchRequestLog.Remove(ABatchRecord)

db.SaveChanges()
db.Dispose()