<asp:ListView ID="ListView1" DataSourceID="SelectDOU" runat="server" DataKeyNames="DOU_id" 
            EnableViewState="false"
            OnItemDataBound="ListView1_ItemDataBound"
            OnItemInserting="ListView1_ItemInserting"
            OnItemCreated="ListView1_ItemCreated"
            OnItemInserted="ListView1_ItemInserted"
            InsertItemPosition="FirstItem">
            <InsertItemTemplate>
            Cайт:
                <asp:TextBox Text='<%#Bind("DOU_Url") %>' runat="server" ID="tBUrl" Width="50%" BackColor="White"></asp:TextBox>

               Вид доу:
                <asp:DropDownList runat="server" ID="EditDOUForm" AppendDataBoundItems="false" EnableViewState="false" Width="50%">
                </asp:DropDownList>
                <asp:RequiredFieldValidator ID="RFValidator5" runat="server"
                    ControlToValidate="EditDOUForm" ErrorMessage="Поле &quotВид доу&quot не выбрано." SetFocusOnError="true"
                Display="Dynamic" Font-Bold="true" ForeColor="Red">
                </asp:RequiredFieldValidator>

                

           <asp:Button runat="server" Text="Добавить" CommandName="Insert" ID="linkbu" CausesValidation="true" OnClick="linkbu_Click">
           </asp:Button>
         <asp:Button runat="server" Text="Отмена" CommandName="Exit" OnClick="Button1_Click" ID="Button1" CausesValidation="false">
         </asp:Button>
          </InsertItemTemplate>
<ItemTamplate></ItemTemplate>
        </asp:ListView>

 protected void ListView1_ItemCreated(object sender, ListViewItemEventArgs e)
    {
        if ((e.Item != null) && (e.Item.ItemType == ListViewItemType.InsertItem))
        {
            DropDownList ddlForm = (DropDownList)e.Item.FindControl("EditDOUForm");
            if (ddlForm != null)
            {
                SqlConnection con = new SqlConnection(ConnectionString);
                SqlCommand cmd = new SqlCommand("DOUForm_select", con);
                cmd.CommandType = CommandType.StoredProcedure;
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds, "DOUForm");
                ddlForm.DataSource = ds.Tables["DOUForm"];
                ddlForm.DataTextField = "DOUForm_name";
                ddlForm.DataValueField = "DOUForm_id";
                ddlForm.DataBind();
                ddlForm.Items.Insert(0, new ListItem("", ""));
            }
        }

protected void ListView1_ItemCreated(object sender, ListViewItemEventArgs e)
    {
        if ((e.Item != null) && (e.Item.ItemType == ListViewItemType.InsertItem))
        {
            DropDownList ddlForm = (DropDownList)e.Item.FindControl("EditDOUForm");
            if (ddlForm != null)
            {
                SqlConnection con = new SqlConnection(ConnectionString);
                SqlCommand cmd = new SqlCommand("DOUForm_select", con);
                cmd.CommandType = CommandType.StoredProcedure;
                SqlDataAdapter da = new SqlDataAdapter(cmd);
                da.Fill(ds, "DOUForm");
                ddlForm.Items.Clear();   //#################### Что бы список не дублировать ###############
                ddlForm.DataSource = ds.Tables["DOUForm"];
                ddlForm.DataTextField = "DOUForm_name";
                ddlForm.DataValueField = "DOUForm_id";
                ddlForm.DataBind();
                ddlForm.Items.Insert(0, new ListItem("", ""));
            }
        }