Imports System.IO
Imports DevExpress.XtraPrinting

Public Class ReportCreator
    Private Envelope As Envelope

    Public Sub New(pEnvelope As Envelope)
        Envelope = pEnvelope
    End Sub

    Public Async Function CreateReport(pReportItems As List(Of ReportItem)) As Task(Of Byte())
        Dim oItems = pReportItems.Select(AddressOf MergeEnvelope).ToList()
        Dim oSource As New ReportSource With {.Items = oItems}
        Dim oReport As New rptEnvelopeHistory() With {.DataSource = oSource, .DataMember = "Items"}

        Await oReport.CreateDocumentAsync()

        Using oStream As New MemoryStream()
            Await oReport.ExportToPdfAsync(oStream, New PdfExportOptions)
            Return oStream.ToArray()
        End Using
    End Function

    Private Function MergeEnvelope(pItem As ReportItem) As ReportItem
        If pItem.Envelope Is Nothing Then
            pItem.Envelope = Envelope
        End If
        Return pItem
    End Function
End Class