Dropdownlist with autopostback="true" showing 1st item on selecting any item

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C#

DropDownList

ASP.NET4

I have two dropdownlists:- "ddl1" and "ddl2". "ddl2" is populated on selectedindexchange event of "ddl1" i.e. at runtime. "ddl1" and "ddl2" both have Autopostback="true". "ddl2" also has selectedindexchange event handled. But when I try to select an item in "ddl2" it refreshes the page and it shows the 1st item in the "ddl2". I have searched it on the internet and tried various things like putting "ddl2" in update panel, and handling prerender event of pagelifecycle, but they didn't help. Please provide some solution. It is required for my project. Please help

What I have tried:

I have searched it on the internet and tried various things like putting "ddl2" in update panel, and handling prerender event of pagelifecycle, but they didn't help. I have also tried setting enableviewstate="True" and ViewStateMode="Enabled" without any luck.