at page load i couldnt set textbox text ?

Hello

I have below codes. But i couldnt set textbox value at page load.  when i clickk imagebutton, i do response then i need to set textbox value at page load. Thanks. Note : I use ajax autocomplete for textbox.

protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {

        ViewState["textbox"] = txtMovie.Text;
        Response.Redirect("Default.aspx");
    }
   protected void Page_Load(object sender, EventArgs e)
    {

        txtMovie.Focus();
        ViewState["txt"] = "";


        try
        {
            if (!Page.IsPostBack)
            {
                ViewState["txt"] = ViewState["textbox"];
                txtMovie.Text = ViewState["textbox"].ToString();
            }
        }
        catch { }
        searchbutton();
         }