Determining the Control(User Control) that Caused a PostBack and reading value from querystring.....How?

Hi,

I have a web user control(a datalist with paging support).It just read some values from query string(for paging support).I have two instance of same user control on the a page.Just assume with ID Control1 and Control2. Both these control read value from query string like department id and perform operation according to that.If Control1  cause post back query string get changed and value read in Control1.Now problem starts Control2  is also reading this value from query string.Which i do not want.I just want if post back is performed by Control1 only that control read value from querystring not other control.

 I hope you got my problem.Solution will be to know which instance of user control cause postback(Control1 or Control2).Means if Control1 cause postback then only that can read query string.

Thanks.
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