Populate Dropdown list based on another dropdown list [duplicate]

Answer 1

1 Set AutoPostBack="true" on first DropDownList1 and add OnSelectIndexChanged="YourDelegate".

2 In your delegate when you post data, bind your second DropDownList2 with prefix SelectedValue

 protected void DropDownList_SelectedIndexChanged(object sender, EventArgs e)
 {
   var value =  DropDownList1.SelectedValue;
   if(value == "Product1")
   { 
    ....      
   }
   else if(value == "Product2")
   { 
    ....      
   }
 }