How to do OnClick on selected item in “dynamic” ASP.NET DropDownList without using JavaScript

Currently, there is 2 values in my DropDownList which is viewProduct and editProduct. So when the user selects one of the value, it will direct user to the particular function in ASP.NET. I have tried OnSelectedIndexChanged, but it seems like not working on the dynamic DropDownList.
Here is my code: