The problem is because you are storing the string name instead of the actual value!
protected void Page_Load(object sender, EventArgs e)
{
sNo = (string)Request.QueryString["no"].Trim();
sYear = (string)Request.QueryString["Year"].Trim();
Session["Year"] = "sYear";
Session["no"] = "sNo";
}
Use the following instead:
protected void Page_Load(object sender, EventArgs e)
{
sNo = (string)Request.QueryString["no"].Trim();
sYear = (string)Request.QueryString["Year"].Trim();
Session["Year"] = sYear;
Session["no"] = sNo;
}