Selected index changed not working

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ASP.NET4

I have a dropdown list that populates on first run with code.
The autopostback is true, but the selectedindexchanged event is not firing.
Can someone please help me?

What I have tried:

<pre><asp:DropDownList ID="dproy" runat="server" Width="180px" AutoPostBack="True" AppendDataBoundItems="true" OnSelectedIndexChanged="dproy_SelectedIndexChanged1" CausesValidation="True" OnTextChanged="dproy_TextChanged" ViewStateMode="Enabled">
                        </asp:DropDownList>

protected void dproy_SelectedIndexChanged1(object sender, EventArgs e)
{
idproy = dproy.SelectedIndex.ToString();
lbl1.Text = idproy;
}