ALTER procedure [dbo].[SpUserLogin]
@Email nvarchar(100),
@Password nvarchar(15)
as
Begin
select count(Email) from Student_Main_Email
where [Email]=@Email and [Password]=@Password

Union All
select count(Email) from Faculty_Reviewer_Email
where [Email]=@Email and [Password]=@Password
End

protected void Login_button_Click(object sender, EventArgs e)
    {
        string connectionstring = "Data Source=NADIR\SQLEXPRESS;Initial Catalog=PHD_System_new;Integrated Security=True";
        SqlConnection con = new SqlConnection(connectionstring);
        con.Open();
        SqlCommand cmd = new SqlCommand("SpUserLogin", con);
        SqlParameter paramusername = new SqlParameter("@Email", Login_Email.Value);
        SqlParameter parampassword = new SqlParameter("@Password", Login_Password.Value);
        cmd.Parameters.Add(paramusername);
        cmd.Parameters.Add(parampassword);

        cmd.CommandType = CommandType.StoredProcedure;

        int returncode = (Int32)cmd.ExecuteScalar();

        if (returncode == 1)
        {
            Session["LoginUserName"] = Login_Email.Value;

            Server.Transfer("WebForm1.aspx");
            //lblMessage.Text = "User Name or Password is valid.";

        }
        else {
            lblMessage.Text = "Invalid User Name or Password.";
        }
        con.Close();
    }