Question: I'm wondering if it is possible to use the OpenCV framework to recognise a building? 
For example, if I store an image of a building, is it possible to use OpenCV to detect this building through the iPhone camera?

Thanks!

Answer: 
You need to use **Ajax Control Tool kit's Cascaded Drop-down**

Here is the like for it:

<http://www.asp.net/AjaxLibrary/AjaxControlToolkitSampleSite/Walkthrough/CCDWithDB.aspx>

and here is the demo:

<http://www.asp.net/AjaxLibrary/AjaxControlToolkitSampleSite/CascadingDropDown/CascadingDropDown.aspx>

here is a tutorial link:

<http://www.dotnetfox.com/articles/ajax-cascading-dropdown-example-with-database-in-Asp-Net-1078.aspx>

Hope this material helps.
You have to set AutoPostBack="true" to the first drop down list and clear other drop downs items before adding new item.

**ASPX:**

```
<asp:DropDownList ID="ddl_UOM" runat="server" OnSelectedIndexChanged="ddl_UOM_SelectedIndexChanged" AutoPostBack="true">
        <asp:ListItem Text="Amount" Value="Amount"></asp:ListItem>
        <asp:ListItem Text="PAC" Value="PAC"></asp:ListItem>
        <asp:ListItem Text="Base" Value="Base"></asp:ListItem>
</asp:DropDownList>
<asp:DropDownList ID="ddl_UOM2" runat="server"></asp:DropDownList>
<asp:DropDownList ID="ddl_UOM3" runat="server"></asp:DropDownList>
<asp:DropDownList ID="ddl_UOM4" runat="server"></asp:DropDownList>

```

**ASPX.CS**

```
protected void ddl_UOM_SelectedIndexChanged(object sender, EventArgs e)
    {
        string uom_Name = ddl_UOM.SelectedItem.Value;
        ddl_UOM2.Items.Clear();
        ddl_UOM2.Items.Add(new ListItem(uom_Name, uom_Name));

        ddl_UOM3.Items.Clear();
        ddl_UOM3.Items.Add(new ListItem(uom_Name, uom_Name));

        ddl_UOM4.Items.Clear();
        ddl_UOM4.Items.Add(new ListItem(uom_Name, uom_Name));
    }

```