get datalist values

<ItemTemplate>
<asp:LinkButton id="lnkSelect" Text="Select"
CommandName="Select" runat="server" CommandArgument='<%# Eval("ID") %>'/>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</ItemTemplate>

//find control for the textbox
TextBox TextBox1 =  (TextBox)e.Item.FindControl("TextBox1");
If(e.CommandName=="Select")
{
  //code to get the textbox value based on the ID in command argument. 
}