Redefine AndroidManifest Project Property

I'm trying to conditionally set the AndroidManifest property in my csproj file. (e.g. - normally, use the default value.)

<AndroidManifest>Properties\AndroidManifest.xml</AndroidManifest>

(e.g. - if build configuration is "debug" use...)

<AndroidManifest>Properties\AndroidManifest-Debug.xml</AndroidManifest>

How can I accomplish this?

I've tried a plethora of things, but nothing appears to work. Seems that once the value is set, that's it. Maybe I'm just doing something wrong? I'm using Xamarin Studio on Mac, to be specific, so whatever it is, needs to work for xbuild as well as msbuild.

Any thoughts? Proven examples?