query results into session variable

how do I put query results into session variable?

protected void btnLogin_Click(object sender, EventArgs e)
    {
        String strUserId = txtbxSiteCode.Text.ToString();
        String strPassword = txtbxPassword.Text.ToString();

        if (ValidateUser(strUserId, strPassword))
        {
            //generate a session variable
            SqlCommand cmd = new SqlCommand("uspGetCIDFKBySiteCode", new SqlConnection(myConn));
            cmd.CommandType = System.Data.CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@SiteCode", strUserId);
            cmd.Connection.Open();
            SqlDataReader rdr = cmd.ExecuteReader();
            cmd.Connection.Close();
            cmd.Connection.Dispose();
            //something like?
            //Session["CIDFK"] = Convert.ToInt32(CIDFK.fieldvalue);
            //how do I put the value into a session like this?  Session["CIDFK"] = 30; where the cidfk is an interger
            FormsAuthentication.RedirectFromLoginPage(strUserId, false);
            Response.Redirect("audit/default.aspx");
            //I read that SqlDataReader would do what you want it to and work great for single table returns.
            //You can store them to session variables and access the elements.
            //how is this achieved?
        }
        else
        {
            Response.Redirect("login.aspx", true);
        }
    }

I'm just not sure how to do it.