Accessing Controls Inside ASP.NET View Controls (Event Handling) - asp.net

Question

If I have the following ListView, how can I attach a SelectedIndexChanged event listener to the DropDownList so I can perform a command on the respective object? Imagine I have a list of new users and I want to add them to a usergroup by selecting the group from the DropDownList.
<asp:ListView ID="NewUsers" runat="server" DataSourceID="NewUsersSDS" DataKeyNames="ID">
<LayoutTemplate>
<asp:Table ID="groupPlaceholder" runat="server"><asp:TableRow></asp:TableRow></asp:Table>
</LayoutTemplate>
<GroupTemplate>
<asp:TableCell ID="itemPlaceholder" runat="server"></asp:TableCell>
</GroupTemplate>
<ItemTemplate>
<asp:Table ID="NewUsersTable" runat="server" Width="32%" CssClass="inlineTable">
<asp:TableRow>
<asp:TableCell Width="100px"><%# Eval("FullName").ToString.Trim()%></asp:TableCell>
<asp:TableCell>
<asp:HiddenField ID="RowIndex" runat="server" Value="<%# Container.DisplayIndex %>" />
<asp:DropDownList ID="UserGroupSelect" runat="server" DataSourceID="UserGroupSelectSDS" DataValueField="ID" DataTextField="UserGroup"
OnSelectedIndexChanged="UserGroupSelect_SelectedIndexChanged" AutoPostBack="True">
</asp:DropDownList>
</asp:TableCell>
</asp:TableRow>
</asp:Table>
</ItemTemplate>
</asp:ListView>
I've been having issues accessing controls inside of __View controls. I read in a few places that you could access them by NewUsers.FindControl([ControlID as String]) but this doesn't seem to be working for me. I guess this is what's called a dynamic control? Not really sure, feeling a bit lost.
As always, your help is greatly appreciated. ;)
Additional Info / Code
'Now working code, thanks to James :)
Protected Sub ItemBind(ByVal sender As Object, ByVal e As ListViewItemEventArgs) Handles NewUsers.ItemDataBound
Dim lv As ListView = DirectCast(sender, ListView)
If e.Item.ItemType = ListViewItemType.DataItem Then
lv.DataKeys(e.Item.DataItemIndex).Value.ToString() 'get the datakey
End If
End Sub
Protected Sub UserGroupSelect_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
Dim RowIndex As Integer = CInt(DirectCast(DirectCast(sender, DropDownList).Parent.FindControl("RowIndex"), HiddenField).Value)
Dim pk As Integer = CInt(NewUsers.DataKeys(RowIndex)("ID"))
Try
MessageBox("Update key " + pk.ToString, "Update Key") 'Custom js "alert" box function
Catch ex As Exception
MessageBox("Something went wrong, is the update key empty?")
End Try
End Sub

Answer 1

To access controls in a ListView (or any databound control), you need to use FindControl on the item/row:
ListViewItem item = ListView1.Items[0];
if (item != null)
{
DropDownList ddl = item.FindControl("DropDownList1") as DropDownList;
if (ddl != null)
{
string value = ddl.SelectedValue;
}
}
As for attaching a SelectedIndexChanged event, you can do it like this:
<ItemTemplate>
<asp:DropDownList ID="DropDownList1" runat="server"
AutoPostBack="true"
OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
<asp:HiddenField ID="HiddenField1" runat="server" Value='<%# Container.DisplayIndex %>' />
</ItemTemplate>
Code-behind:
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
int rowIndex = Convert.ToInt32(((HiddenField)((DropDownList)sender).Parent.FindControl("HiddenField1")).Value);
ListViewItem item = ListView1.Items[rowIndex];
if (item != null)
{
//your logic here
}
}
To retrieve a datakey:
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
int rowIndex = Convert.ToInt32(((HiddenField)((DropDownList)sender).Parent.FindControl("HiddenField1")).Value);
int pk = (int)ListView1.DataKeys[rowIndex]["PrimaryKey"];
}