How can I set in a form ID from url?

I have page with film details, for example link: http://localhost:58528/Pages/Film/Details.aspx?filmId=5 and user can add on this page comment from some film, for example film with filmId = 5 - this is my code:
<asp:FormView ID="FormView2" runat="server" ItemType="Project.Models.Comments" DefaultMode="Insert" InsertMethod="InsertComment"> <InsertItemTemplate> <div class="create-comment"> <fieldset> <asp:TextBox ID="TextBox3" runat="server" Text='<%# Bind("FilmId") %>' Enabled="False"></asp:TextBox> <div class="editor-label"> <asp:Label ID="Label1" runat="server" Text="Author"></asp ...