iTextSharp MVC 查看到 PDF

Question

在使用 iTextSharp 时尝试解析要转换为 PDF 的 html 字符串时，我的 TextReader 遇到了一点问题。

Function ViewDeliveryNote(ByVal id As Integer) As FileStreamResult
        'Memory buffer
        Dim ms As MemoryStream = New MemoryStream()

        'the document
        Dim document As Document = New Document(PageSize.A4)

        'the pdf writer
        PdfWriter.GetInstance(document, ms)

        Dim wc As WebClient = New WebClient
        Dim htmlText As String = wc.DownloadString("http://localhost:59800/Warehouse/DeliveryNote/" & id) 'Change to live URL
        Dim worker As html.simpleparser.HTMLWorker = New html.simpleparser.HTMLWorker(document)
        Dim reader As TextReader = New StringReader(htmlText)

        document.Open()

        worker.Open()
        worker.StartDocument()
        worker.Parse(reader)
        worker.EndDocument()
        worker.Close()

        document.Close()

        'ready the file stream
        Response.ContentType = "application/pdf"
        Response.AddHeader("content-disposition", "attachment;filename=DeliveryNote.pdf")
        Response.Buffer = True
        Response.Clear()
        Response.OutputStream.Write(ms.GetBuffer(), 0, ms.GetBuffer.Length)
        Response.OutputStream.Flush()
        Response.End()

        Return New FileStreamResult(Response.OutputStream, "application/pdf")
 End Function

即使StringReader(htmlText) 已成功读取 HTML 页面，它停止的行是 worker.Parse(reader)，错误为 Object reference not set to an instance of an object。

我不确定自己做错了什么或目前缺少什么，因此我将不胜感激。

更新我只是尝试Dim reader As New StringReader(htmlText)，但无济于事。虽然 htmlText 仍然肯定包含一个值，但对象认为它没有。

Answer 1

我肯定会为此编写一个自定义操作结果以避免污染我的控制器。此外，您的代码中所有那些未处理的一次性资源都应该得到照顾：

Public Class PdfResult
    Inherits ActionResult

    Private ReadOnly _id As Integer

    Public Sub New(ByVal id As Integer)
        _id = id
    End Sub

    Public Overrides Sub ExecuteResult(context As ControllerContext)
        If context Is Nothing Then
            Throw New ArgumentNullException("context")
        End If

        Dim response = context.HttpContext.Response
        response.Buffer = True
        response.ContentType = "application/pdf"
        response.AddHeader("Content-Disposition", "attachment; filename=DeliveryNote.pdf")

        Using client = New WebClient()
            Dim htmlText As String = client.DownloadString("http://localhost:59800/Warehouse/DeliveryNote/" & _id) 'Change to live URL
            Dim doc = New Document(PageSize.A4)
            PdfWriter.GetInstance(doc, response.OutputStream)
            Dim worker = New HTMLWorker(doc)
            doc.Open()
            worker.Open()
            Using reader = New StringReader(htmlText)
                worker.Parse(reader)
            End Using
            doc.Close()
        End Using
    End Sub
End Class

然后简单地说：

Function ViewDeliveryNote(ByVal id As Integer) As ActionResult
    Return New PdfResult(id)
End Function

您还应该确保服务器可以访问所需的 url。不要忘记他的请求将在网络帐户的上下文中执行，该帐户可能与普通帐户没有相同的权限。