iTextSharp應用中關於“Cannot access a closed Stream”問題的解決辦法（附帶提供如何在頁面中顯示PDF的流）

假設有這麼一段代碼：        private void CreatePdf()
        {
            Document doc=new Document();
            MemoryStream ms=new MemoryStream();
            PdfWriter writer =PdfWriter.GetInstance(doc,ms);
            doc.Open();
            doc.Add(new Paragraph(DateTime.Now.ToLongDateString()));
            doc.Close();
            ViewPdf(ms);
        }

        private void ViewPdf(Stream fs)
        {
            byte[] buffer=new byte[fs.Length];
            fs.Position=0;            
            fs.Read(buffer,0,(int)fs.Length);
            Response.Clear();
            Response.ContentType = "application/pdf";
            Response.BinaryWrite(buffer);
            Response.OutputStream.Flush();
            Response.OutputStream.Close();
        }

在調用CreatePdf()的時候碰到了如下錯誤：
Cannot access a closed Stream.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ObjectDisposedException: Cannot access a closed Stream.

Source Error:

Line 58: private void ViewPdf(Stream fs) Line 59: { Line 60: byte[] buffer=new byte[fs.Length]; Line 61: fs.Position=0; Line 62: fs.Read(buffer,0,(int)fs.Length);

問題出在哪裡了呢？從錯誤我可以知道我們準備操作的Stream已經關閉，這是因為iTextSharp自動關閉產生的Stream了，那有沒有辦法不關閉呢？
看了下面這段代碼，也許就不用我說什麼了：    private void Page_Load(object sender, System.EventArgs e)
        {
            //CreatePdf();
            EditPDF();
        }

        private void EditPDF()
        {
            PdfReader reader =new PdfReader(@"e:\xml2PDF.pdf");
            MemoryStream ms=new MemoryStream();
            PdfStamper stamper=new PdfStamper(reader,ms);
            stamper.Writer.CloseStream=false;
            PdfContentByte cb=stamper.GetOverContent(1);            
            cb.Circle(250,250,50);
            cb.SetColorFill(iTextSharp.text.Color.RED);
            cb.SetColorStroke(iTextSharp.text.Color.WHITE);
            cb.FillStroke();
            stamper.Close();
            ViewPdf(ms);        
        }

        private void CreatePdf()
        {
            Document doc=new Document();
            MemoryStream ms=new MemoryStream();
            PdfWriter writer =PdfWriter.GetInstance(doc,ms);
            writer.CloseStream=false;
            doc.Open();
            doc.Add(new Paragraph(DateTime.Now.ToLongDateString()));
            doc.Close();
            ViewPdf(ms);
        }

        private void ViewPdf(Stream fs)
        {
            byte[] buffer=new byte[fs.Length];
            fs.Position=0;            
            fs.Read(buffer,0,(int)fs.Length);
            fs.Close();
            Response.Clear();
            Response.ContentType = "application/pdf";
            Response.BinaryWrite(buffer);
            Response.OutputStream.Flush();
            Response.OutputStream.Close();
        }

原來PdfWriter有個熟悉就是讓我們設定是否自動關閉Stream的，而預設是關閉的。

2006-12-01更新ViewPdf function        private void ViewPdf(Stream fs)
        {
            byte[] buffer = new byte[fs.Length];
            fs.Position = 0;
            fs.Read(buffer, 0, (int)fs.Length);
            Response.Clear();
            //Response.AddHeader("Content-Disposition", "attachment;FileName=out.pdf");
            Response.AddHeader("Content-Length",fs.Length.ToString()); 
            Response.ContentType = "application/pdf";
            fs.Close();

            Response.BinaryWrite(buffer);
            Response.OutputStream.Flush();
            Response.OutputStream.Close();
        } 

如果需要下載而不是在IE中看的話，請把Response.AddHeader("Content-Disposition", "attachment;FileName=out.pdf");前的注釋去掉，並替換上你想要的名字。

如果不指定Response.AddHeader("Content-Length",fs.Length.ToString());，IE會把網頁內容也輸出，在PDF後面，此時顯示產生的PDF被破壞（這個說是IE的一個bug，我也不清楚）
如果附件名為中文：
Response.AddHeader("Content-Disposition", "attachment;FileName="+HttpUtility.UrlEncode("中文.pdf"));

內嵌顯示PDF
Response.AddHeader("Content-Disposition", "inline;FileName=out.pdf");

更多這方面的資訊google上搜尋吧。

另外一個和緩衝有關的資訊，Cache-Control，需要的自己研究下吧。