Getting control that fired postback in page_init

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>