Site template

I want to fetch the site template used to create a site programmatically.
I struggled a lot there. Finally i find a way.

SPWeb.WebTemaplate and SPWeb.Configuration.
It is ok for default sites (site templates available by default in Sharepoint.)

Consider my scenario:
I created a site using custom template( importing a custom wsp file test.wsp to Solutions area of site collection)
Now I want to get the site template used to create the above site in the format like "guid#test" which is in the format similar to the SPSite.GetCustomWebTemplates function.

I used the same combination SPWeb.WebTemaplate and SPWeb.Configuration.But it results the STS#1 or STS#0 which is not the template i used (test.wsp). How can i get it?

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AArunKumar