nant directory::exists returns false even though directory exists -

i'm trying check if directory exists part of nant script , getting false negative. here script fragment:

<echo message="${backup.dir} --> ${directory::exists('${backup.dir}')}"/> 

here output:

[echo] d:\d\rtc\backup\20110223 --> false 

except directory exists.

as side note if run..

<echo message="${backup.dir} --> ${directory::get-creation-time('${backup.dir}')}"/> 

i following error:

expression: ${backup.dir} --> ${directory::get-creation-time('${backup.dir}')}                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^     not find part of path "d:\d\rtc\${backup.dir}". 

and if run..

<echo message="directory name --> ${path::get-directory-name('${backup.dir}')}"/> 

i get

[echo] directory name --> 

all in i'm confused right now.. thoughts?

you must not use ${} in nested way:

<echo message="${backup.dir} --> ${directory::exists(backup.dir)}"/>