Combobox OnSelectedIndexChanged not firing

Question

Hello,

I have two combo box and want to fill second combo based on first's selected value. I've added OnSelectedIndexChanged event for first combo and set its auto post-back property to true.Now when use select any value from 1st combo,  OnSelectedIndexChanged will call . And its working right now.

But When I set selected value of combo box from code behind ,I want to fire OnSelectedIndexChanged event.

combobox.selectedvalue= 1;

Currently in my application OnSelectedIndexChanged event not firing when above line is executed.

If anybody knows how to solve this then please tell me.

-Thanks