求助！用户控件问题

我的用户控件里面的代码：
<asp:FormView ID="FormView1" runat="server" Width="250px">
                       <ItemTemplate>
                           <div class="loadperson">
                               <div class="loadinfo">您好，<span id="username"><%#Eval("user_name") %><span><span id="span"><asp:HyperLink ID="HyperLink1" NavigateUrl="admin/Default.aspx"  runat="server">管理后台</asp:HyperLink></span></div>
                               <div class="loadinfo">上次登录时间:<span id="time"><%#Session["time"].ToString () %></span></div>
                             <div class="loadinfo">上次登录地址:<span id="Span1"><%#Session["loadaddress"].ToString () %></span></div>
                               <div class="loadinfo">本次登录地址:<span id="time"><%#Eval ("user_loadaddress")%></span></div>
                               <div class="loadinfo">
                                   <a href="#">编辑个人信息</a></div>
                               <div class="loadinfo">
                                   <asp:LinkButton ID="cancellogin" runat="server" onclick="cancellogin_Click">退出</asp:LinkButton></div>
                           </div>
                       </ItemTemplate>
                   </asp:FormView>用户控件后台代码：
 protected void BindToFormView()
    {
        if (Session["yonghu"] != null && Session["yonghu"].ToString() != "")
        {
            this.HyperLink2.Text = "dsdsd";
            if (Users.UserById(Convert.ToInt32(Session["yonghu"])).Tables[0].Rows[0]["user_role"].ToString() != "4")
            {                ((HyperLink)this.FormView1.FindControl("HyperLink1")).Visible = true;
            }
            this.FormView1.DataSource = Users.UserById(Convert.ToInt32(Session["yonghu"]));
            this.FormView1.DataBind();
            MultiView1.ActiveViewIndex = 1;        }
    }
原本运行时报错未将对象引用到实例，报错代码是((HyperLink)this.FormView1.FindControl("HyperLink1")).Visible = true;
不知道是为什么