Display Message(Saved Successfully) and Pass session to another page in ASP.Net

Sir All Code is Not Present With me

Sample.Cs( Backend Code)

void ShowMessaage(String msg) { ClientScript.RegisterStartupScript(Page.GetType(), "", "<script language='javascript'> alert('" + msg + "');</script>"); }

Save_buttonClick{

cmd.ExecuteNonQuery();  ShowMessaage(" Record Added SucessFully !!!"); 

Session["LastName"] = txtlName.Text;

Response.Redirect("Default2.aspx");

}

When i Pass SessionThat time MY MessageBox Does Not Show my message But It Shows Message When I Removed Session Passing Code