Is PdfStamper disposing output stream? (iTextSharp)

问题

I am using iTextSharp to add page numbers to a PDF with C#. While running code analysis the MemoryStream for the output is suspected to be disposed more than once. See this warning generated by Visual Studio. Is this an API problem? Should the second parameter of PdfStamper be marked as out? Is there a way for me to fix this warning?

MemoryStream mem = null;
PdfReader reader = null;
PdfStamper stamper = null;
try
{
    mem = new MemoryStream();
    reader = new PdfReader(m_pdf);                
    stamper = new PdfStamper(reader, mem);

    // do stuff
    stamper.Close();
    var result = mem.ToArray();
}
finally
{
    if(stamper != null)
    {
        stamper.Dispose();
    }

    if (reader != null)
    {
        reader.Dispose();
    }

    if (mem != null)
    {
        mem.Dispose();
    }
}

回答1:

This isn't really an answer but to expand upon what @mkl said, switch over to using directives since those perform the try/finally stuff for you automatically.

Below is the way I (and probably everyone else that uses iTextSharp) would generally recommend to interact with iTextSharp. The outer using is BCL stuff, in this case the MemoryStream and the inner using statements are iTextSharp stuff.

//Will hold our raw PDF bytes
Byte[] result;

//BCL stuff first
using (var mem = new MemoryStream()) {

    //iText stuff in the middle
    using (var reader = new PdfReader(m_pdf)) {
        using (var stamper = new PdfStamper(reader, mem)) {
            // do stuff

        }
    }

    //iText is completely done and disposed of at this point
    //so we can now grab the raw bytes that represent a PDF
    result = mem.ToArray();
}

As an aside, not necessarily for the OP but just in case someone else sees this, there is almost never (and by "almost never" I really mean "never") a good reason to not close the underlying stream. You can read from the stream by grabbing the raw bytes and writing to it again never makes sense.

回答2:

The following allowed me to keep the MemoryStream open after the stamper is closed:

pdfStamper.Writer.CloseStream = false;

来源：https://stackoverflow.com/questions/29141804/is-pdfstamper-disposing-output-stream-itextsharp

标签

itextsharp

itext

code-analysis

idisposable