I have a datalist with a linkbutton listing outlet names. How do I get outletID?

[Til Athers]

In my ASP.net page, I have the datalist and this template:
<ItemTemplate>
<asp:ImageButton ID="btnButton" runat="server" OnClick="lnkBtnOutlet_Click" ImageUrl="/images/button.gif"
width="22" />
<asp:LinkButton ID="lnkBtnOutlet" runat="server" CssClass="style55"
Text='<%# Eval("outletName") %>' OnClick="lnkBtnOutlet_Click"></asp:LinkButton>
</ItemTemplate>

In C#, I have:
protected void lnkBtnOutlet_Click(object sender, EventArgs e)
{
try
{
LinkButton btn = sender as LinkButton;
TextBox1.Text = btn.Text;
Session["OUTLET_ID"] = ...;
Response.Redirect("Details.aspx?OutletID=" + ...);
}
catch { }
}

How do I get the equivalent outletID of the outletName? I know it's part of the data structure I load in my datalist, but how do I get it?