There are no direct trains between Yeshwantpur and Bangalore Cantonment, so this is not feasible.As Dheeraj said, Yeshwantpur station to Benson town is under 10 kms, there is no need at all to go towards Bangalore city Junction. I would strongly suggest you to hire a cab in case you have heavy luggage. Even if you intend to travel by BMTC city bus, it involves the headache of changing of two buses to Benson town.
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And as addy1280 pointed out, even try buying new ticket from Yeshwantpur stn to Cantonment stn and then catch an auto. addy can confirm if this feasible.
There is a Metro station right next to the Yeshwantpur station, but the Metro line does not go anywhere near Benson town. You can take the Metro, get down at Sampige Road Malleshwaram and then take an auto. But that is not worth it (unless you want to take a ride in the new Metro). Instead of that I would suggest taking a prepaid auto or a cab from Yeshwantpur railway station.What about the Bangalore metro?? Do they have any stations nearby??