I'd say that reflecting into the LGPL lib is a 'combined work' and so is subject to the limitations described in the licence:
A “Combined Work” is a work produced by combining or linking an
Application with the Library. The particular version of the Library
with which the Combined Work was made is also called the “Linked
The “Minimal Corresponding Source” for a Combined Work means the
Corresponding Source for the Combined Work, excluding any source code
for portions of the Combined Work that, considered in isolation, are
based on the Application, and not on the Linked Version.
The “Corresponding Application Code” for a Combined Work means the
object code and/or source code for the Application, including any data
and utility programs needed for reproducing the Combined Work from the
Application, but excluding the System Libraries of the Combined Work.
So, given these definitions (where your reflecting into the library is equivalent to linking with it and the code that does the reflection is the minimal corresponding source) you have to follow this section:
- Combined Works.
You may convey a Combined Work under terms of your choice that, taken
together, effectively do not restrict modification of the portions of
the Library contained in the Combined Work and reverse engineering for
debugging such modifications, if you also do each of the following:
d) Do one of the following:
0) Convey the Minimal Corresponding Source under the terms of this License, and the Corresponding Application Code in a form suitable for, and under terms that permit, the user to recombine or relink the Application with a modified version of the Linked Version to produce a modified Combined Work, in the manner specified by section 6 of the GNU GPL for conveying Corresponding Source.
1) Use a suitable shared library mechanism for linking with the Library. A suitable mechanism is one that (a) uses at run time a copy of the Library already present on the user's computer system, and (b) will operate properly with a modified version of the Library that is interface-compatible with the Linked Version.
so I'd say (Note: IANAL) you'd have to release the reflecting code part of your app under the LGPL too, though the section of your app that uses that code can still be proprietary.