无法访问pdf生成中的封闭流

Question

当我尝试使用具有多个表的iTextSharp构建PDF文件时,我收到以下错误消息:

无法访问封闭的Stream.

这是我的代码:

//Create a byte array that will eventually hold our final PDF
Byte[] bytes;

List<TableObject> myTables = getTables();
TableObject currentTable = new TableObject();

//Boilerplate iTextSharp setup here
//Create a stream that we can write to, in this case a MemoryStream
using (MemoryStream ms = new MemoryStream())
{
    //Create an iTextSharp Document which is an abstraction of a PDF but **NOT** a PDF
    using (Document doc = new Document(PageSize.A4, 10f, 10f, 10f, 0f))
    {
        foreach (TableObject to in myTables)
        {
            //Create a writer that's bound to our PDF abstraction and our stream
            using (PdfWriter writer = PdfWriter.GetInstance(doc, ms))
            {
                if (!doc.IsOpen())
                {
                    //Open the document for writing
                    doc.Open();
                }
                //Get the data from database corresponding to the current tableobject and fill all the stuff we need!
                DataTable dt = getDTFromID(to._tableID);
                Object[] genObjects = new Object[5];
                genObjects = gen.generateTable(dt, currentTable._tableName, currentTable._tableID.ToString(), currentTable, true);

                StringBuilder sb = (StringBuilder)genObjects[1];
                String tableName = sb.ToString();
                Table myGenTable = (Table)genObjects[0];
                String table = genObjects[2].ToString();

                using (StringReader srHtml = new StringReader(table))
                {
                    //Parse the HTMLiTextSharp.tool.xml.XMLWorkerHelper.GetInstance().ParseXHtml(writer, doc, srHtml);
                }

                //should give empty page at the end, need to fix it later
                doc.NewPage();
            }

        }
        doc.Close();
    }

    //After all of the PDF "stuff" above is done and closed but **before** we
    //close the MemoryStream, grab all of the active bytes from the stream
    bytes = ms.ToArray();
}

//Now we just need to do something with those bytes.
Response.ContentType = "application/pdf";
Response.AppendHeader("Content-Disposition", "attachment; filename=Report_complete.pdf");
Response.BinaryWrite(bytes);

这是我的asp.net应用程序中的完整堆栈跟踪:

[ObjectDisposedException:无法访问已关闭的Stream.]
System.IO .__ Error.StreamIsClosed()+57
System.IO.MemoryStream.Write(Byte [] buffer,Int32 offset,Int32 count)+11011171 iTextSharp.text.pdf.OutputStreamCounter.写(Byte []缓冲区,Int32偏移量,Int32计数)+52
iTextSharp.text.pdf.PdfIndirectObject.WriteTo(Stream os)+53
iTextSharp.text.pdf.PdfBody.Write(PdfIndirectObject indirect,Int32 refNumber,Int32 generation)+ 100
iTextSharp.text.pdf.PdfBody.Add(PdfObject objecta,Int32 refNumber,Int32 generation,Boolean inObjStm)+385
iTextSharp.text.pdf.PdfWriter.AddToBody(PdfObject objecta,PdfIndirectReference refa)+51
iTextSharp.text.pdf.Type1Font .WriteFont(PdfWriter writer,PdfIndirectReference piref,Object [] parms)+317
iTextSharp.text.pdf.FontDetails.WriteFont(PdfWriter writer)+296
iTextSharp.text.pdf.PdfWriter.AddSharedObjectsToBody()+180
iTextSharp.text.pdf. PdfWriter.Close(
)+ 86 iTextSharp.text.DocWriter.Dispose()+10
System.Web.Util.CalliEventHandlerDelegateProxy.Callbac k(Object sender,EventArgs e)+51 System.Web.UI.Control.OnLoad(EventArgs e)+92
System.Web.UI.Control.LoadRecursive()+54
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint ,Boolean includeStagesAfterAsyncPoint)+772

本bytes-阵列应该是使用语句中accessable,但它看起来像有错误.

我试过foreach在using(writer ...)块内移动循环:

//Create a byte array that will eventually hold our final PDF
//must be outside of the foreach loop (and everything else), because we store every single generated table in here for the final pdf!!
Byte[] bytes;

List<TableObject> myTables = getTables();
TableObject currentTable = new TableObject();

//Boilerplate iTextSharp setup here
//Create a stream that we can write to, in this case a MemoryStream
using (MemoryStream ms = new MemoryStream())
{
    //Create an iTextSharp Document which is an abstraction of a PDF but **NOT** a PDF
    using (Document doc = new Document(PageSize.A4, 10f, 10f, 10f, 0f))
    {
            //Create a writer that's bound to our PDF abstraction and our stream
            using (PdfWriter writer = PdfWriter.GetInstance(doc, ms))
            {
                //loop all tableobjects inside the document & the instance of PDFWriter itself! 
                foreach (TableObject to in myTables)
                {
                    //only happens on the first run!
                    if (!doc.IsOpen())
                    {
                        //Open the document for writing
                        doc.Open();
                    }
                    //Get the data from database corresponding to the current tableobject and fill all the stuff we need!
                    DataTable dt = getDTFromID(to._tableID);
                    Object[] genObjects = new Object[5];
                    genObjects = gen.generateTable(dt, currentTable._tableName, currentTable._tableID.ToString(), currentTable, true);

                    StringBuilder sb = (StringBuilder)genObjects[1];
                    String tableName = sb.ToString();
                    Table myGenTable = (Table)genObjects[0];
                    String table = genObjects[2].ToString();

                    using (StringReader srHtml = new StringReader(table))
                    {
                        //Parse the HTML
                        iTextSharp.tool.xml.XMLWorkerHelper.GetInstance().ParseXHtml(writer, doc, srHtml);
                    }

                    //this will probably render a whole new page at the end of the file!! need to be fixed later!!!
                    doc.NewPage();
                }
                //After all of the PDF "stuff" above is done and closed but **before** we
                //close the MemoryStream, grab all of the active bytes from the stream
                bytes = ms.ToArray();
            }
        doc.Close();
    }


}

//Now we just need to do something with those bytes.
Response.ContentType = "application/pdf";
Response.AppendHeader("Content-Disposition", "attachment; filename=ShiftReport_complete.pdf");
Response.BinaryWrite(bytes);

但我仍然得到同样的错误.

Answer 1

PdfWriter默认关闭流.只需在PdfWriter.GetInstance之后添加以下行

writer.CloseStream = false;

Answer 2

解决方案很简单，只需将 a 放入循环.ToList()中的我的集合中即可foreach：

foreach (TableObject to in myTables.ToList())
{
     //some code stuff

这个问题下的这个答案帮助我解决了这个问题。