在单击图像按钮时设置会话变量

页面上有两个图像按钮。当单击其中一个时，它需要在页面返回之前设置会话变量yesID和NoId。我试着把代码在每个按钮的点击事件，但页面再次加载之前，它运行在点击事件的代码。我如何设置2会话变量时，任何图像被点击?

  <div id="MainPics">
        <div id="RightPic">
            <p>
                <asp:Label ID="FirstPicMemberNameLabel" runat="server" Text="" Font-Bold="True" ForeColor="White"></asp:Label>
            </p>
            <asp:ImageButton ID="FirstPicLink" Width="90%" runat="server" 
                onclick="FirstPicLink_Click" />
        </div>
        <div id="LeftPic">
            <p>
                <asp:Label ID="SecondPicMemberNameLabel" runat="server" Text="" ForeColor="White" Font-Bold="True"></asp:Label>
            </p>
            <asp:ImageButton ID="SecondPicLink" Width="90%" runat="server" 
                onclick="SecondPicLink_Click" />
        </div>
        <div id="skip">
            <asp:LinkButton ID="LBNoChoice" PostBackUrl="~/default.aspx" ForeColor="White" runat="server">Skip - I Can't Choose</asp:LinkButton>
        </div>
    </div>

代码隐藏页

   protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            Session["yesID"] = 0;
            Session["noId"] = 0;
        }
        else
        {
            //Send Session Variables to Database for Storage.
        }    
 }
  protected void FirstPicLink_Click(object sender, ImageClickEventArgs e)
    {
        Session["yesID"] = 1;
        Session["noId"] = 2;
    }
    protected void SecondPicLink_Click(object sender, ImageClickEventArgs e)
    {
        Session["yesID"] =2;
        Session["noId"] = 1;
    }

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        Session["yesID"] = 0;
        Session["noId"] = 0;
    }
    //else
    //{
        //Send Session Variables to Database for Storage.
    //}
}
protected void FirstPicLink_Click(object sender, ImageClickEventArgs e)
{
    Session["yesID"] = 1;
    Session["noId"] = 2;
    SendSessionVariables(Session["yesID"], Session["noId"]);
}
private void SendSessionVariables(object p, object p_2)
{
    // Your database code here
}
protected void SecondPicLink_Click(object sender, ImageClickEventArgs e)
{
    Session["yesID"] = 2;
    Session["noId"] = 1;
    SendSessionVariables(Session["yesID"], Session["noId"]);
}