Populate (Bind) DropDownList from existing sharepoint list using C# in ASP.Net

ok i solved the to poputate the dropdown.

using Microsoft.SharePoint;
using System;
using System.ComponentModel;
using System.Web.UI.WebControls.WebParts;
using System.Linq;
using Microsoft.SharePoint.Utilities;
using System.Web.UI.WebControls;

namespace Lavorazioni.Crm.WP.GestioneAttivita
{
    [ToolboxItemAttribute(false)]
    public partial class GestioneAttivita : WebPart
    {
        // Uncomment the following SecurityPermission attribute only when doing Performance Profiling on a farm solution
        // using the Instrumentation method, and then remove the SecurityPermission attribute when the code is ready
        // for production. Because the SecurityPermission attribute bypasses the security check for callers of
        // your constructor, it's not recommended for production purposes.
        // [System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Assert, UnmanagedCode = true)]
        public GestioneAttivita()
        {
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
            InitializeControl();
        }


        protected void Page_Load(object sender, EventArgs e)
        {
            // _id = Page.Request.QueryString["ID"];
            if (!Page.IsPostBack)
            {
                SPSecurity.RunWithElevatedPrivileges(delegate ()
                {
                    using (SPSite ElevatedSite = new SPSite(SPContext.Current.Web.Site.ID))
                    using (SPWeb ElevatedWeb = ElevatedSite.OpenWeb(SPContext.Current.Web.ID))
                    {
                       CaricaTendinaAttivita(ElevatedWeb);
                       CaricaTendinaEsito(ElevatedWeb);
                       CaricaTendinaCausale(ElevatedWeb);
                        CaricaItem(ElevatedWeb);


                    }
                });
            }
        }

        protected void btnSeleziona_Click(object sender, EventArgs e)
        {
            SPSecurity.RunWithElevatedPrivileges(delegate ()
            {
                using (SPSite ElevatedSite = new SPSite(SPContext.Current.Web.Site.ID))
                using (SPWeb ElevatedWeb = ElevatedSite.OpenWeb(SPContext.Current.Web.ID))
                {
                    CaricaItem(ElevatedWeb);
                    FiltraRisultati(ElevatedWeb);
                }
            });
        }

        protected void btnAnnulla_Click(object sender, EventArgs e)
        {
            SPSecurity.RunWithElevatedPrivileges(delegate ()
            {
                using (SPSite ElevatedSite = new SPSite(SPContext.Current.Web.Site.ID))
                using (SPWeb ElevatedWeb = ElevatedSite.OpenWeb(SPContext.Current.Web.ID))
                {
                    PulisciControlli();
                    CaricaItem(ElevatedWeb);
                }
            });
        }

       private void PulisciControlli()
        {

            ddlAttivita.SelectedValue = "";
            ddlEsito.SelectedValue = "";
            ddlCausale.SelectedValue = "";
            txtUtente.Text = "";
            txtOrigineCSV.Text = "";
        }


        private void CaricaItem(SPWeb web)

        {
            SPList listaGestAtt = web.GetList(web.ServerRelativeUrl + "/Lists/" + ddlListaDiRiferimento.Text);          
            SPListItemCollection items = listaGestAtt.GetItems();



            var itemBindabili = from SPListItem i in items.Cast<SPListItem>()
                                select new
                                {
                                    ID = i.ID, 
                                    Titolo = i["Title"],
                                    Attivita = new SPFieldLookupValue(i["Attivit_x00e0_"] as String).LookupValue, 
                                    OrigineCSV = new SPFieldLookupValue(i["OrigineCSV"] as String).LookupValue,
                                    IDUtente = ControllaID(web, Convert.ToString(i["Utente"])),
                                    Utente = ControllaUtente(web, Convert.ToString(i["Utente"])),
                                    Esito = new SPFieldLookupValue(i["Esito"] as String).LookupValue,
                                    Causale = new SPFieldLookupValue(i["Causale"] as String).LookupValue
                                };

            grdItems.DataSource = itemBindabili.ToList();
            grdItems.DataBind();
        }




        private string ControllaUtente(SPWeb web, string fieldValue)
        {
            if (!string.IsNullOrEmpty(fieldValue))

                return new SPFieldUserValue(web, fieldValue).User.Name;

            else
                return (fieldValue);
        }      

        private int ControllaID(SPWeb web, string fieldValue)
        {
            if (!string.IsNullOrEmpty(fieldValue))

                return new SPFieldUserValue(web, fieldValue).User.ID;

            else
                return -1;
        }

        protected void ddlListaDiRiferimento_SelectedIndexChanged(object sender, EventArgs e)
        {

            string value = ddlListaDiRiferimento.SelectedValue;

            //in base al primo valore bindi la griglia
            CaricaItem(SPContext.Current.Web);
        }


         private void CaricaTendinaAttivita(SPWeb Elevatedweb)
         {
            SPList list = Elevatedweb.Lists.TryGetList("Attività");
            SPQuery query = new SPQuery();
            query.Query = "<OrderBy><FieldRef Name='ID' Ascending='TRUE' /></OrderBy>";
            SPListItemCollection collection = list.GetItems(query);
            ddlAttivita.DataSource = collection;
            ddlAttivita.DataTextField = "Title";
            ddlAttivita.DataValueField = "ID";
            ddlAttivita.Items.Insert(0, new ListItem("---Select---", "0"));
            ddlAttivita.DataBind();
        }


        private void CaricaTendinaEsito(SPWeb Elevatedweb)
        {
            SPList list = Elevatedweb.Lists.TryGetList("Esiti");
            SPQuery query = new SPQuery();
            query.Query = "<OrderBy><FieldRef Name='ID' Ascending='TRUE' /></OrderBy>";
            SPListItemCollection collection = list.GetItems(query);
            ddlEsito.DataSource = collection;
            ddlEsito.DataTextField = "Title";
            ddlEsito.DataValueField = "ID";
            ddlEsito.Items.Insert(0, new ListItem("---Select---", "0"));
            ddlEsito.DataBind();
        }


        private void CaricaTendinaCausale(SPWeb Elevatedweb)
        {
            SPList list = Elevatedweb.Lists.TryGetList("Specifica");
            SPQuery query = new SPQuery();
            query.Query = "<OrderBy><FieldRef Name='ID' Ascending='TRUE' /></OrderBy>";
            SPListItemCollection collection = list.GetItems(query);
            ddlCausale.DataSource = collection;
            ddlCausale.DataTextField = "Title";
            ddlCausale.DataValueField = "ID";
            ddlCausale.Items.Insert(0, new ListItem("---Select---", "0"));
            ddlCausale.DataBind();
        }

        private void FiltraRisultati(SPWeb web)
        {
            SPList listaGestAtt = web.GetList(web.ServerRelativeUrl + "/Lists/" + ddlListaDiRiferimento.Text);
            var value = ddlAttivita.SelectedItem.Text;
            SPQuery query = new SPQuery();
            query.Query = "<Where><Contains><FieldRef Name='Attivit_x00e0_' /><Value Type='Text'>" + ddlAttivita.SelectedItem.Text + "</Value></Contains></Where>";
            
             var items = listaGestAtt.GetItems(query);

            grdItems.DataSource = items;
            grdItems.DataBind();
        }
    }
}

<h1>Gestione Attività</h1>

<asp:Label ID="lblListaDiRiferimento" runat="server" Text="Lista di riferimento"></asp:Label>
<asp:DropDownList ID="ddlListaDiRiferimento" runat="server" OnSelectedIndexChanged="ddlListaDiRiferimento_SelectedIndexChanged" AutoPostBack="true">
    <asp:ListItem Text="CVT-FINDOMESTIC" Value="CVTFINDOMESTIC"></asp:ListItem>
    <asp:ListItem Text="RCAPRIMIRINNOVI-VW" Value="RCAPRIMIRINNOVIVW"></asp:ListItem>
    <asp:ListItem Text="RCASECONDIRINNOVI-RCI" Value="RCASECONDIRINNOVIRCI"></asp:ListItem>
    <asp:ListItem Text="RCASECONDIRINNOVI-VW" Value="RCASECONDIRINNOVIVW"></asp:ListItem>
    <asp:ListItem Text="CONGIUNTI-VW" Value="CONGIUNTIVW"></asp:ListItem>
    <asp:ListItem Text="CVT-OPEL" Value="CVTOPEL"></asp:ListItem>
    <asp:ListItem Text="CVT-VW" Value="CVTVW"></asp:ListItem>
    <asp:ListItem Text="RCA-VERTI" Value="RCAVERTI"></asp:ListItem>
    <asp:ListItem Text="--" Value=""></asp:ListItem>
</asp:DropDownList>
<br />
<br />
<asp:Literal ID="lblAttivita" runat="server" Text="Attività"></asp:Literal>
<asp:DropDownList ID="ddlAttivita" runat="server"></asp:DropDownList>
<br />
<br />
<asp:Literal ID="lblEsito" runat="server" Text="Esito"></asp:Literal>
<asp:DropDownList ID="ddlEsito" runat="server"></asp:DropDownList>
<br />
<br />
<asp:Literal ID="lblCausale" runat="server" Text="Causale"></asp:Literal>
<asp:DropdownList ID="ddlCausale" runat="server"></asp:DropdownList>
<br />
<br />
<asp:Literal ID="lblUtente" runat="server" Text="Utente"></asp:Literal>
<asp:TextBox ID="txtUtente" runat="server"></asp:TextBox>
<br />
<br />
<asp:Literal ID="lblOrigineCSV" runat="server" Text="OrigineCSV"></asp:Literal>
<asp:TextBox ID="txtOrigineCSV" runat="server"></asp:TextBox>
<br />
<br />
<asp:Button ID="btnSelezionaTitle" runat="server" Text="Cerca" OnClick="btnSeleziona_Click"/>
<asp:Button ID="btnAnnulla" runat="server" Text="Annulla" OnClick="btnAnnulla_Click"/>
<br />
<br />



<asp:GridView ID="grdItems" runat="server" AutoGenerateColumns="false" PageSize="10" AllowPaging="true" DataKeyNames="ID" >
    <Columns>
        <asp:CommandField ShowSelectButton="true" DeleteText="Seleziona Record"/>
        <asp:BoundField DataField="Titolo" HeaderText="Titolo" />
        <asp:BoundField DataField="Attivita" HeaderText="Attività" />
        <asp:BoundField DataField="OrigineCSV" HeaderText="OrigineCSV" />
        <asp:BoundField DataField="IDUtente" HeaderText="IDUtente" />
        <asp:BoundField DataField="Utente" HeaderText="Utente" />
        <asp:BoundField DataField="Esito" HeaderText="Esito" />
        <asp:BoundField DataField="Causale" HeaderText="Causale" />     
    </Columns>
</asp:GridView>