how to check if page is refreshed in asp.net

bool IsPageRefresh = false;

//this section of code checks if the page postback is due to genuine submit by user or by pressing "refresh"
if (!IsPostBack)     
{
    ViewState["ViewStateId"] = System.Guid.NewGuid().ToString();
    Session["SessionId"] = ViewState["ViewStateId"].ToString();
}
else
{
    if (ViewState["ViewStateId"].ToString() != Session["SessionId"].ToString())
    {
        IsPageRefresh = true;
    }

    Session["SessionId"] = System.Guid.NewGuid().ToString();
    ViewState["ViewStateId"] = Session["SessionId"].ToString();
}