A non-persistent file?

[wolfgang.woegerer]

I have a pdf document saved (as a base64 encoded string) in a remote
database. I now want to allow the client application to display that
document. Because of legal issues I am not allowed to temporarily save
the pdf document on the local hard disk.

My question: Is there a way in C# and the .net framework to display
the pdf document, say in the Acrobat Reader, without saving the pdf
file to hard disk?

At a first glance I would say no. The Acrobat Reader needs the path to
a file name as an argument. And how could we tell the Acrobat Reader
at what location in memory the file would start?!

But on a second glance, maybe there is a part of the Windows operating
system that has some kind of unique file name (or some kind of handle)
and allows some kind of a data stream. Just an idea.

Thanks in advance,
Wolfgang

 

[Nicholas Paldino [.NET/C# MVP]]

Wolfgang,

I would think that you need something like a device driver in order to
do this. Basically, the device driver would handle the opening of the file
for you (you would create a file which doesn't exist, but would use your
driver to stream the content to Adobe) and stream the data to Adobe.

However, developing device drivers is not something you can do in .NET.

Does Acrobat not have a mechanism to stream the content to the reader?

 

[Ignacio Machin ( .NET/ C# MVP )]

At a first glance I would say no. The Acrobat Reader needs the path to
a file name as an argument. And how could we tell the Acrobat Reader
at what location in memory the file would start?!

But on a second glance, maybe there is a part of the Windows operating
system that has some kind of unique file name (or some kind of handle)
and allows some kind of a data stream. Just an idea.

Somewhere in the back of my head I have the idea that windows support
a kind of isolated storage , or something like that you could use to
save the file into.

Your problem though is the reader, if you find a component that
display a pdf (I think there are some around) you could display it
directly from your app and most probably without saving it to hdd.

 

[Ciaran O''Donnell]

The .NET isolated storage is still saved on the FileSystem, it is put in the
users profile area in Documents and Settings in the Application Data folder
or somewhere like that. The only option for this would be to find a PDF
viewer component that can open a PDF from a stream rather than from a file.
You would need to check this with the authors and check that it doesnt save
it to a temporary file to do it too.

Let us know if you find one that does it as it would be good to know for the
future.

 

[Chakravarthy]

Wolfgang,

First things first, it is not possible to stream the data to a PDF reader.

Secondly, if you have to invoke the PDF reader, there has to be a file.
thus, with out writing onto disk, you can't achieve this task.

HTH

 

[Paul H]

I have a pdf document saved (as a base64 encoded string) in a remote
database. I now want to allow the client application to display that
document. Because of legal issues I am not allowed to temporarily save
the pdf document on the local hard disk.

My question: Is there a way in C# and the .net framework to display
the pdf document, say in the Acrobat Reader, without saving the pdf
file to hard disk?

You could use some kind of RAM disk, but this requires installing drivers.

 

[Pavel Minaev]

Wolfgang,

First things first, it is not possible to stream the data to a PDF reader..

Secondly, if you have to invoke the PDF reader, there has to be a file.
thus, with out writing onto disk, you can't achieve this task.

This isn't quite correct - Windows allows to use named pipes in calls
to CreateFile, so, as long as a program doesn't try to seek the
stream, it should be able to read from / write to a named pipe. For
example, you can use "type" to read from a pipe. Then, .NET
application can use NamedPipeServerStream to provide the data.

I very much doubt it would work with any PDF reader, though.

 

[Peter Bromberg [C# MVP]]

The only way I can think of is to have the source application send the
stream via HTTP to say, a WebBrowser control in the client app with the
correct Response.ContentType. This would trigger the Acrobat Reader to come
up and display the PDF in the browser window.
Peter