Chunk data into 2k chunks and update in Sql.

Bulk insert VB

'''This code just saved 6700 mergecodes across to the db in a few second compared to long minutes via EF :)
Public Shared Sub SaveMany(Items As List(Of BranchContact))
        If Items Is Nothing Then Return
        Using db As New LogIQEntities
            Dim chunkedItems = ChunkData(Items, 500) 'I've not tested to see the upper/lower bounds of benefits/deficits on this figure :P
            For Each chunkedList In chunkedItems
                Dim Query = New StringBuilder
                For Each i In chunkedList
                    Query.Append($"update BranchContacts set Mergecodes = '{i.Mergecodes}' where Emailid =  {i.Emailid} and Branch = '{i.Branch}';")
                Next
                db.Database.ExecuteSqlCommand(Query.ToString)
            Next
            ' db.SaveChanges()
        End Using
    End Sub

    Public Shared Iterator Function ChunkData(Of T)(source As IEnumerable(Of T), chunkSize As Integer) As IEnumerable(Of IEnumerable(Of T))
        Dim _chunkSize = If(source.Count < chunkSize, source.Count, chunkSize)
        Dim i = 0
        While i < source.Count()
            Yield source.Skip(i).Take(_chunkSize)
            i += _chunkSize
        End While
    End Function