I am trying to get data from stored procedure and its working but I can't make it work when I try to get more than one data and make it a table. I always get "IndexOutOfRangeException" and I believe its because of return function, here is the code :

using System;
            using System.Collections.Generic;
            using System.Linq;
            using System.Threading.Tasks;
            using System.Data.SqlClient;
            using System.Collections;

        namespace NetWebApp.Model
    {
         public class InvoiceModel
    {
        public string ReferenceNumber { get; set; }
        public string AllocationType { get; set; }
        public string Contract { get; set; }
        public string EP { get; set; }
        public string json;
        public IEnumerable<ItemModel> Items { get; set; }

            public static InvoiceModel Example()
        {
            ArrayList objs = new ArrayList();

            SqlConnection sqlConnection1 = new SqlConnection("Data 
            Source=localhost\\VANDERSQL2K8R2;Initial 
            Catalog=PGPL_GMS_DEV;User ID=admin;Password=Password");  
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "[Approval].[rspSelAllocationSetupModification] '287','systemAdmin'";

            cmd.Connection = sqlConnection1;
            sqlConnection1.Open();

            SqlDataReader rdr = cmd.ExecuteReader();
            // Data is accessible through the DataReader object here.
            rdr.Read();
            
                return new InvoiceModel()
                    { // I success to cal these data
                        ReferenceNumber = rdr["ReferenceNumber"].ToString(),
                        AllocationType = rdr["AllocationTypeName"].ToString(),
                        Contract = rdr["ContractNumber"].ToString(),
                        EP = rdr["AllocationPeriod"].ToString(),

                        Items = new List<ItemModel>()
                    {
                     //whenever I try to call these data (item model), they got me error
                     //"IndexOutOfRangeException"

                      new ItemModel() {
                        AG = rdr["AllocationCategory"].ToString(),
                        AP = rdr["AllocationParameter"].ToString(),
                        CAM = rdr["CurrentAllocationMethod"].ToString(),
                        CF = rdr["CurrentAllocationFormula"].ToString(),
                        NAM = rdr["NewAllocationMethod"].ToString(),
                        NF = rdr["NewAllocationFormula"].ToString()
                }
        
                    }
                    };

            sqlConnection1.Close();
            
            }
    }

    public class ItemModel
    {
        public string AG { get; set; }
        public string AP { get; set; }
        public string CAM { get; set; }
        public string CF { get; set; }
        public string NAM { get; set; }
        public string NF { get; set; }
        public string json { get; set; }
    }}

I use https://github.com/jsreport/jsreport-dotnet-example-webapp as references.
can anyone help ? Please .....
thank you in advance