How to select the Data Source at Runtime in SSRS Report Builder

Question

before going to problem let me clear that i know there are similar questions ask before but could not find the answer of my problem. my problem is:
I want to select the

Answer 1

You can't use a Shared Data Source with a dynamic data source. Use an embedded one. I think it's to prevent you from corrupting other reports' data sources.

http://www.keepitsimpleandfast.com/2012/08/how-to-use-dynamic-data-sources-in-your.html