iTextSharp应用中关于“Cannot access a closed Stream”问题的解决办法（附带提供如何在页面中显示PDF的流）

假设有这么一段代码：

        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();
        }

在调用CreatePdf()的时候碰到了如下错误：

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);

问题出在哪里了呢？从错误我可以知道我们准备操作的Stream已经关闭，这是因为iTextSharp自动关闭生成的Stream了，那有没有办法不关闭呢？
看了下面这段代码，也许就不用我说什么了：

    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();
        }

原来PdfWriter有个熟悉就是让我们设置是否自动关闭Stream的，而默认是关闭的。

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();
        } 

如果需要下载而不是在IE中看的话，请把Response.AddHeader("Content-Disposition", "attachment;FileName=out.pdf");前的注释去掉，并替换上你想要的名字。

如果不指定Response.AddHeader("Content-Length",fs.Length.ToString());，IE会把网页内容也输出，在PDF后面，此时显示生成的PDF被破坏（这个说是IE的一个bug，我也不清楚）
如果附件名为中文：
Response.AddHeader("Content-Disposition", "attachment;FileName="+HttpUtility.UrlEncode("中文.pdf"));

内嵌显示PDF
Response.AddHeader("Content-Disposition", "inline;FileName=out.pdf");

更多这方面的信息google上搜索吧。

另外一个和缓存有关的信息，Cache-Control，需要的自己研究下吧。