Redirected I/O with GnuPG?

[Robert J. Hansen]

I'm hitting a stumbling block trying to write a small snippet of C# 
which fetches information about cipher preferences.  Since I've not been 
able to find information about the keyring file format, I'm falling back 
to using GnuPG to do the keyring parsing.  This is a suboptimal 
solution, but it'll do for reasonably small keyrings.

The problem is that for some reason I'm entirely unable to read in 
anything from GnuPG's output.  I'm invoking GnuPG as:

    gpg --command-fd 0 --status-fd 2 --no-tty --edit-key <keyID>

While I'm able to receive status messages on standard error, any attempt 
to read any amount of data from standard output will block indefinitely.

This is not a Windows-specific problem: I've tried under Win32, OS X and 
Linux.

Is there some magic command-line flag I'm missing here?  Has anyone had 
similar experiences writing code which invokes GnuPG?