问iTextsharp -在AcroFields.SetField之后如何获得可编辑的字段？

EN

                ' flatten the form to remove editting options, set it to false
                ' to leave the form open to subsequent manual edits
                pdfStamper.FormFlattening = False

Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
    Dim newFile As String = Me.Text.Replace(".pdf", "_Out.pdf")

    ' create w/overwrite copy of the template
    Dim pdfReader As New PdfReader(pdfTemplate)
    Dim pdfStamper As New PdfStamper(pdfReader, New FileStream(newFile, FileMode.Create))

    pdfFormFields = pdfStamper.AcroFields

    ' set form pdfFormFields ' field names are case sensitive
    pdfFormFields.SetField("NAME", "Firstname Lastname")
    pdfFormFields.SetField("PHONE", "805.555.1212")

    '' report by reading values from completed PDF
    Dim sTmp As String = "Completed: " + pdfFormFields.GetField("NAME") + " " + _
    pdfFormFields.GetField("PHONE")
    MessageBox.Show(sTmp, "Finished")

    ' flatten the form to remove editting options, set it to false
    ' to leave the form open to subsequent manual edits
    pdfStamper.FormFlattening = False

    ' close the pdf
    pdfStamper.Close()
End Sub