Get SSRS report dataset/datatable which is being bind with report?

I have a situation where we have to work with report in three different ways:
1- preview in the Report Viewer
2- download pdf of report
3- download csv (not from report export button) because that will download whole report as it is being render in report, but in my situation we have to download actual data which is being bind with report. because in report we generally Alias apart from actual name so we want external csv which download actual dataset/datatable which is being use in report.

Eventually we can separately call stored procedures that will give the same result as it should be but according to my project architecture code will go duplicate. So i am asking this question.