OutOfMemoryException when creating large ZIP file using System.IO.Packaging

Question

I am trying to debug an OutOfMemoryException that occurs when creating a fairly large ZIP file using System.IO.Packaging.ZipPackage.

The code is iterating through a large list of objects, doing the following for each object.

1. Serializing the object data to a temporary file.
2. Creating a PackagePart for the file.
3. Copy from a source System.IO.Stream to another:
   • Source stream: FileStream
   • Target stream: PackagePart::GetStream() => MS.Internal.IO.Zip.ZipIOModeEnforcingStream

Finally it calls Package::Close() which saves the file.

The problem I am having is that for a particularly large list of objects, I am seeing an OutOfMemoryException (the x86 process size is getting to about 1.2GB in size).

I was thinking about partitioning the object data into chunks so I only process a smaller amount per loop (i.e. steps 1-3 above). The idea is that I would create n ZIP files in a temporary directory, and then find a way to combine them into a single archive.

Is this possible using System.IO.Packaging? What would I use to combine the parts?

Or is there a better way to fix this?

Answer 1

Calling the Flush method on the Package object in between creating a new package should probably solve the problem as that would cause the memory buffer to be flushed to disk.