pageindexchanging issue

Question

Hi everybody. 

I have a gridview with pagination which is displaying filtered data from sql server. I have also a button. When this one is clicked, it's displaying all the data from sql server. My problem is that when I want to click on page 2, only the filtered data are displaying and not the second page of the total data.

 

Here is my code aspx:

                <asp:Button ID="btnTteLivraisons" CssClass="btn btn-success" runat="server" Text="Toutes les livraisons" OnClick="btnTteLivraisons_Click" Visible="False"  />


                                HeaderStyle-CssClass="header" RowStyle-CssClass="rows" AllowPaging="True"
                                OnPageIndexChanging="GridView1_PageIndexChanging" OnSorting="GridView1_Sorting"
                                AutoGenerateColumns="False"  CellPadding="4"
                                ForeColor="#333333" GridLines="None" Width="100%">
                                <SelectedRowStyle BackColor="#C5BBAF" />
                                <AlternatingRowStyle BackColor="White" />

                                <HeaderStyle HorizontalAlign="center" />
                                <Columns>
                                    <asp:BoundField DataField="Nom" HeaderText="Nom" ItemStyle-HorizontalAlign="center" />
                                    <asp:BoundField DataField="Prenom" HeaderText="Prénom" ItemStyle-HorizontalAlign="center" />
                                    <asp:BoundField DataField="CP" HeaderText="Code Postal" ItemStyle-HorizontalAlign="center" />
                                    <asp:BoundField DataField="ville" HeaderText="Ville" ItemStyle-HorizontalAlign="center" />
                                    <asp:BoundField DataField="Telephone" HeaderText="Téléphone" ItemStyle-HorizontalAlign="center" />
                                    <asp:BoundField DataField="date_command2" HeaderText="Date Commande" DataFormatString="<%$AppSettings:FormatDateGrille%>" ItemStyle-HorizontalAlign="center" />
                                    <asp:BoundField DataField="heure_command" HeaderText="Heure Commande" ItemStyle-HorizontalAlign="center" />
                                    <asp:BoundField DataField="montantCommande" HeaderText="Montant de la Commande" ItemStyle-HorizontalAlign="center" />
                                    <asp:TemplateField HeaderText="">
                                        <ItemTemplate>
                                            <asp:Button id="btnCommande" runat="server" Text="Détail Commande" OnClick="btnCommande_Click"  CommandArgument='<%# Eval("ID") %>' class="btn btn-info" />
                                        </ItemTemplate>
                                    </asp:TemplateField>
                                    <asp:TemplateField HeaderText="">
                                        <ItemTemplate>
                                            <asp:Button id="btnEdit" runat="server" Text="Editer" OnClick="Edit" CommandArgument='<%# Eval("ID") %>' class="btn btn-primary" />
                                        </ItemTemplate>
                                    </asp:TemplateField>
                                    <asp:TemplateField HeaderText="">
                                        <ItemTemplate>
                                            <asp:Button ID="btnSupprimer" runat="server" Text="Supprimer" OnClick="Delete" CommandArgument='<%# Eval("ID") %>' CssClass="btn btn-danger" />
                                        </ItemTemplate>
                                    </asp:TemplateField>
                                </Columns>
                            </asp:GridView>

 my code behind :

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                BindInfoLivraison();
                btnTteLivraisons.Visible = true;
            }
        }

public static DataTable ToDataTable<T>(List<T> items)
        {
            DataTable dataTable = new DataTable(typeof(T).Name);

            //Get all the properties
            PropertyInfo[] Props = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
            foreach (PropertyInfo prop in Props)
            {
                //Setting column names as Property names
                dataTable.Columns.Add(prop.Name);
            }
            foreach (T item in items)
            {
                var values = new object[Props.Length];
                for (int i = 0; i < Props.Length; i++)
                {
                    //inserting property values to datatable rows
                    values[i] = Props[i].GetValue(item, null);
                }
                dataTable.Rows.Add(values);
            }
            //put a breakpoint here and check datatable
            return dataTable;
        }

        private void BindInfoLivraison()
        {
            using (RestauDBEntities1 db = new RestauDBEntities1())
            {
                if (db.InfoLivraison.Count() > 0)
                {
                    DateTime today = Convert.ToDateTime(DateTime.Now.ToString("dd/MM/yyyy"));

                    List<InfoLivraison> list = (from infoLiv in db.InfoLivraison where infoLiv.date_command2 == today select infoLiv).ToList();

                    DataTable dt = ToDataTable<InfoLivraison>(list);

                    ViewState["livraison"] = dt;

                    GridView1.DataSource = dt;
                    GridView1.DataBind();

                }
                else
                {
                    GridView1.DataSource = null;
                    GridView1.DataBind();
                }
            }
        }

        private void BindInfoLivraisonTotal()
        {
            DataTable dt = new DataTable();
            using (RestauDBEntities1 db = new RestauDBEntities1())
            {
                if (db.InfoLivraison.Count() > 0)
                {
                    //string today = DateTime.Now.ToString("d");
                    GridView1.DataSource = (from infoLiv in db.InfoLivraison select infoLiv).ToList();
                    GridView1.DataBind();
                }
                else
                {
                    GridView1.DataSource = null;
                    GridView1.DataBind();
                }
            }
        }

protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
        {
            if (ViewState["livraison"] != null)
            {
                GridView1.PageIndex = e.NewPageIndex;
                GridView1.DataSource = ViewState["livraison"];
                GridView1.DataBind();
  }
          }