ASP.NET

my problem is how to display selected item and a content of textbox in a gridview after a submit button dynamically (i will repeat more than 1 time) and so automatically the submit button will insert data in DB(entity framework)
the DropDownList1 is populated from db
to explain more this is my page :

<fieldset id="Item2">
<legend> Item Information</legend>
<br />
<br />
<center>
<table>
<tr>
<td>
<asp:Label ID="lblIemName" runat="server" >Item Name</asp:Label>
</td>
<td>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true"
        AppendDataBoundItems="true" EnableViewState="true">
<asp:ListItem Value="0">--Select--</asp:ListItem></asp:DropDownList>
</td>
</tr>
<tr>
<td>
<asp:Label ID="lblQuantity" runat="server" >Quantité</asp:Label>
</td>
<td>
<asp:TextBox ID="txtQuantity" runat="server" Width="62px"></asp:TextBox></td>
<td><asp:ImageButton ID="btnAddItem" runat="server" Height="20" Width="20" ImageUrl="~/Images/Add.png"  OnClick="btnAddItem12_click"  />
</td>
</tr>
</table>
</center>
<br />
<br />
<center>
<asp:GridView ID="gvPurchasedItem" runat="server" AutoGenerateColumns="False" DataKeyNames="IDItemLinePurchased"
                 BackColor="Aquamarine">
                <Columns>
                    <asp:BoundField HeaderText="CategoryName" ControlStyle-Width="250" DataField="CategoryName">
                        <ControlStyle Width="250px"></ControlStyle>
                    </asp:BoundField>
                    <asp:BoundField HeaderText="ItemName" DataField="ItemName" />
                    <asp:BoundField HeaderText="Quantity" DataField="Quantity" />
                </Columns>
            </asp:GridView>
            </center>
</fieldset>

my behind code is :


protected void Page_Load(object sender, EventArgs e)
        {

            if (!IsPostBack)
            {
                Populateddlitem();
            }
        }

void Populateddlitem()
        {
            DropDownList1.DataTextField = "ItemName";
            DropDownList1.DataValueField = "IDItem";
            DropDownList1.DataSource = LogicItem.Instance.GetItems();
            DropDownList1.DataBind();
        }

protected void btnAddItem_click(object sender, ImageClickEventArgs e)
        {
           // insert bloc
            ItemLinePurchased res = null;
            if (ID == 0)
                res = new ItemLinePurchased();
            else res = LogicItemLinePurchased.Instance.GetItemLinePurchasedByID(ID);
            res.Quantity = Convert.ToInt32(txtQuantity10.Text);
            res.IDItem = Convert.ToInt32(DropDownList1.SelectedItem.Value);
            ViewState["ddl"] = DropDownList1.SelectedItem.Value;
            res.IDPurchasesDoc = Convert.ToInt32(ViewState["PurchasesDocid"]);
            res.State = "IsActive";
            LogicItemLinePurchased.Instance.SaveItemLinePurchased(res);
            int aaa = DropDownList1.SelectedIndex;
            int bbb = Convert.ToInt32(Session["ddlState"]);
            ViewState["id"] = res.IDItemLinePurchased;
            //display grid view
            gvPurchasedItem.DataSource = (from ItemLinePurchased in LogicItemLinePurchased.Instance.GetAllItemLinePurchased()
                                          where ItemLinePurchased.IDItemLinePurchased == Convert.ToInt32(ViewState["id"]) && ItemLinePurchased.State == "IsActive"
                                          select new
                                          {
                                              ItemLinePurchased.IDItemLinePurchased,
                                              ItemLinePurchased.Item.Category.CategoryName,
                                              ItemLinePurchased.Item.ItemName,
                                              ItemLinePurchased.Quantity,
                                          }).ToList();
            gvPurchasedItem.DataBind();
        }
any one have a solution to my problem post it and thanks

Public Function GetChannelForService(ByVal source As String, ByRef loger As Logger) As IStayAtWorkService
    Dim channel As IStayAtWorkService = Nothing
    Dim objStayAtWorkService As IStayAtWorkService = Nothing
    Dim factory As ChannelFactory(Of IStayAtWorkService)
    loger.log(1, "Begin GetClaimRequestContactFromSession, StayAtWorkServiceAddress" + source)
    Try
        Dim result = String.Empty
        'Get the channel from WCF
        Dim address As EndpointAddress = New EndpointAddress(source)
        Dim binding As WSHttpBinding = New WSHttpBinding()
        binding.MaxReceivedMessageSize = 2147483647
        binding.ReaderQuotas.MaxArrayLength = 2147483647
        binding.MaxBufferPoolSize = 2147483647
        binding.SendTimeout = New TimeSpan(1, 1, 1)
        binding.ReceiveTimeout = New TimeSpan(1, 1, 1)
        'binding.CloseTimeout = New TimeSpan(1, 1, 1)
        'binding.OpenTimeout = New TimeSpan(1, 1, 1)
        If factory Is Nothing Then
            factory = New ChannelFactory(Of IStayAtWorkService)(binding, address)
        ElseIf factory.State = CommunicationState.Closed Then
            factory = New ChannelFactory(Of IStayAtWorkService)(binding, address)
        End If
        channel = factory.CreateChannel()
        'Dim tempObj As IStayAtWorkService = channel
        'objStayAtWorkService = DeepClone(tempObj)
        'If (Not factory.State = CommunicationState.Closed) Then
        '    factory.Close()
        'ElseIf factory.State = CommunicationState.Faulted Then
        '    factory.Abort()
        'End If
    Catch ex As Exception
        loger.log(1, "Catch GetChannelForService, Excelption : " + ex.ToString())
    Finally
    End Try
    Return channel
    'Return objStayAtWorkService
End Function