How to programmatically POST data to an aspx page?

Hi everyone,
I'm trying to POST data to an aspx page.

I've got a button click event (btnSend_Click) within which I want to programmatically POST data ("key1=value1", "key2=value2") to another aspx page ("ReceivingPage.aspx") on my site.  It would be very easy to do if it were a GET, cos I'd just append the data key/values to a query string of a HyperLink control. But How do I do this as a POST? 
Thanks for the help. 
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