Getting control that fired postback in page_init - asp.net

Question

I have a gridview that includes dynamically created dropdownlist. When changing the dropdown values and doing a mass update on the grid (btnUpdate.click), I have to create the controls in the page init so they will be available to the viewstate. However, I have several other buttons that also cause a postback and I don't want to create the controls in the page init, but rather later in the button click events.
How can I tell which control fired the postback while in page_init? __EVENTTARGET = "" and request.params("btnUpdate") is nothing

Answer 1

It is possible to determine which control caused a PostBack by looking at Request.Form["__EVENTTARGET"]. The problem with this is that button ids will not show unless you set their UseSubmitBehavior to false. Here's an example:
.aspx.cs
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack)
{
switch (Request.Form["__EVENTTARGET"].ToString())
{
case "ddlOne":
break;
case "btnOne":
break;
case "btnTwo":
break;
}
}
}
.aspx
<form id="form1" runat="server">
<asp:DropDownList ID="ddlOne" AutoPostBack="true" runat="server">
<asp:ListItem Text="One" Value="One" />
<asp:ListItem Text="Two" Value="Two" />
</asp:DropDownList>
<asp:Button ID="btnOne" Text="One" UseSubmitBehavior="false" runat="server" />
<asp:Button ID="btnTwo" Text="Two" UseSubmitBehavior="false" runat="server" />
</form>