State Management :: Sending Paramater Using Session But Its Doesn't Work?

I got the viewCustomer.aspx page sending parameter to EditBusiness.aspx page as per below coding .

After that i retrieved to EditBusiness.aspx.cs by using (Request.QueryString["customerId"] ) and save in session . Then i tried to use the session in the EditPersonal.aspx and EditOther.aspx is worked but then back to EditBusiness.aspx the customerId parameter is disappeared . I believe is because in EditBusiness.aspx.cs using string customerId = Request.QueryString["customerId"] . Even I have tried cookies but its doesnt work .

ViewCustomer.aspx.cs
protected void grdCustomer_RowCommand(object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "Mod")
{
Response.Redirect("EditBusiness.aspx?customerId=" + e.CommandArgument.ToString().Trim() + "&mod=Modify");
}
EditBusiness.aspx.cs
string customerId = Request.QueryString["customerId"]
Session["customerId"] = customerId.ToString();
EditPersonal.aspx.cs and EditOther.aspx.cs
string customerId = Session["customerId"].ToString();
qry = "select *from customer where customerId = " + customerId;