Schedule and post comments to FaceBook wall using ASP.Net

Hi

i want to develop application like hootsuite . com

Schedule the FaceBook wall using ASP.Net

main question :

once user login in my system then he need to add his facebook user name and password once then how can i store that user's FB username and password because they need to Schedule and post comments to FaceBook wall so every time user will not login

can any once guide step by step ?

i hope you all help me

Thanks
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