Could not find control 'x' in ControlParameter 'y'

Question

I'm trying to filter results using a dropdownlist for my listview.

I have altered the select query for the datasource as follows...

The listview:

<asp:AccessDataSource ID="AccessDataSource1" runat="server" 
        DataFile="~/App_Data/ASPNetDB.mdb" 
        SelectCommand="SELECT * FROM [tblNames] WHERE Surnames=@Surnames">
        <SelectParameters>
            <asp:ControlParameter ControlID="DropDownList1" Name="Surnames" 
                PropertyName="SelectedValue" />
        </SelectParameters>
    </asp:AccessDataSource>

The dropdownlist:

<asp:DropDownList ID="DropDownList1" runat="server" 
        DataSourceID="AccessDataSource2" DataTextField="Genre" 
        DataValueField="NameID" AppendDataBoundItems="true">
            <asp:ListItem Value="" Selected ="True" >All Surnames</asp:ListItem>
</asp:DropDownList>

    <asp:AccessDataSource ID="AccessDataSource2" runat="server" 
        DataFile="~/App_Data/ASPNetDB.mdb" SelectCommand="SELECT * FROM [tblSurnames]">
    </asp:AccessDataSource>

The correct Control name is used (the exact same caps as well), but the page on load returns Could not find control 'DropDownList1' in ControlParameter 'Surnames'.

Any suggestions on what I'm doing wrong here?

EDIT: Here is the stack trace if it helps

[InvalidOperationException: Could not find control 'DropDownList1' in ControlParameter 'Surname'.]
   System.Web.UI.WebControls.ControlParameter.Evaluate(HttpContext context, Control control) +2107838
   System.Web.UI.WebControls.Parameter.UpdateValue(HttpContext context, Control control) +50
   System.Web.UI.WebControls.ParameterCollection.UpdateValues(HttpContext context, Control control) +113
   System.Web.UI.WebControls.SqlDataSource.LoadCompleteEventHandler(Object sender, EventArgs e) +46
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   System.Web.UI.Page.OnLoadComplete(EventArgs e) +9010786
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2350

Answer 1

The ControlID needs to be prefixed with the ID of the ContentPlaceHolder which contains the DropDownList:

<asp:ControlParameter 
   Name="Surnames" 
   ControlID="ContentPlaceholderID$DropDownList1" 
   PropertyName="SelectedValue" 
/>

See also: https://stackoverflow.com/a/5719348/124386