Cannot get/use ControlParameter from GridView in a TemplateField SELECT statement - asp.net

Question

I have a simple GridView (with an ID of 'GridViewAttribs') which displays some values from a database.
Within my GridViewAttribs I wish to have a (nested?) ListView but for some reason I cannot use the asp:ControlParameter ControlID="GridViewAttribs" PropertyName as no results are returned in my (nested) ListView.
If I do NOT use the ControlParameter and hardcode my SELECT statement for the ListView, everything works as expected.
Here's my code:
<asp:SqlDataSource ID="SqlDataSourceAttribHeadings" runat="server"
ConnectionString="<%$ ConnectionStrings:customer_support_devConnectionString %>"
ProviderName="<%$ ConnectionStrings:customer_support_devConnectionString.ProviderName %>"
SelectCommand="SELECT equipment_attrib_heading_id, equipment_model_id, equipment_attrib_name FROM equipment_new_attrib_headings WHERE (equipment_model_id = #equipment_model_id) AND (equipment_attrib_heading_deleted = 0) ORDER BY equipment_attrib_name">
<SelectParameters>
<asp:SessionParameter DefaultValue="" Name="equipment_model_id"
SessionField="EquipmentModelID" Type="Int32" />
</SelectParameters>
</asp:SqlDataSource>
<asp:GridView ID="GridViewAttribs" runat="server" AutoGenerateColumns="False"
CellPadding="4" DataKeyNames="equipment_attrib_heading_id"
DataSourceID="SqlDataSourceAttribHeadings" ForeColor="#333333" GridLines="None"
style="margin-right: 0px">
<AlternatingRowStyle BackColor="White" ForeColor="#284775" />
<Columns>
<asp:BoundField DataField="equipment_attrib_heading_id"
HeaderText="equipment_attrib_heading_id" ReadOnly="True"
SortExpression="equipment_attrib_heading_id" />
<asp:BoundField DataField="equipment_model_id" HeaderText="equipment_model_id"
SortExpression="equipment_model_id" />
<asp:BoundField DataField="equipment_attrib_name"
HeaderText="equipment_attrib_name" SortExpression="equipment_attrib_name" />
<asp:TemplateField HeaderText="equipment_attrib_value_details" SortExpression="equipment_attrib_value_details">
<ItemTemplate>
<asp:SqlDataSource ID="SqlDataSourceAttribValues" runat="server"
ConnectionString="<%$ ConnectionStrings:customer_support_devConnectionString %>"
ProviderName="<%$ ConnectionStrings:customer_support_devConnectionString.ProviderName %>"
SelectCommand="SELECT [equipment_attrib_value_details] FROM [equipment_new_attrib_values] WHERE (equipment_attrib_heading_id = #head_id) AND (equipment_id = #equipment_id) AND (equipment_attrib_value_deleted = 0)">
<SelectParameters>
<asp:QueryStringParameter Name="equipment_id" QueryStringField="id"
Type="Int32" />
<asp:ControlParameter ControlID="GridViewAttribs"
Name="head_id" PropertyName="SelectedDataKey.Values[equipment_attrib_heading_id]" Type="Int32" />
</SelectParameters>
</asp:SqlDataSource>
<asp:ListView ID="ListViewAttribValues" runat="server"
DataSourceID="SqlDataSourceAttribValues">
<EmptyDataTemplate>
<table runat="server" style="">
<tr><td>No data was returned.</td></tr>
</table>
</EmptyDataTemplate>
<ItemTemplate>
<tr style="">
<td><asp:Label ID="equipment_attrib_value_detailsLabel" runat="server" Text='<%# Eval("equipment_attrib_value_details") %>' /></td>
</tr>
</ItemTemplate>
<LayoutTemplate>
<table ID="itemPlaceholderContainer" runat="server" border="0" style="">
<tr ID="itemPlaceholder" runat="server">
</tr>
</table>
</LayoutTemplate>
</asp:ListView>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
The GridView displays all columns fine except the "equipment_attrib_value_details" column where I get "No data was returned."
However, if I take out the asp:ControlParameter which calls upon #head_id and use this hardcoded SELECT statement then I see the correct (albeit hardcoded) values:
SelectCommand="SELECT [equipment_attrib_value_details] FROM [equipment_new_attrib_values] WHERE (equipment_attrib_heading_id = 3) AND (equipment_id = #equipment_id) AND (equipment_attrib_value_deleted = 0)">
Therefore, for some reason, it would appear that the GridViewAttribs value of "equipment_attrib_heading_id" is not being passed to / picked up by the nested asp:ControlParameter
On the off chance, I've also tried replacing:
PropertyName="SelectedDataKey.Values[equipment_attrib_heading_id]"
With:
PropertyName="SelectedValue"
But this didn't resolve the issue either, still not data was returned.
If it helps, I'm using Visual Studio 2010 with ASP.NET4 (vb).

Answer 1

What you could try is using a hidden field and use that control for the controlparameter
<asp:TemplateField HeaderText="equipment_attrib_value_details" SortExpression="equipment_attrib_value_details">
<ItemTemplate>
<asp:HiddenField runat="server" ID="heading_id" Value='<%# Eval("equipment_attrib_heading_id") %>' />
<asp:SqlDataSource ID="SqlDataSourceAttribValues" runat="server"
ConnectionString="<%$ ConnectionStrings:customer_support_devConnectionString %>"
ProviderName="<%$ ConnectionStrings:customer_support_devConnectionString.ProviderName %>"
SelectCommand="SELECT [equipment_attrib_value_details] FROM [equipment_new_attrib_values] WHERE (equipment_attrib_heading_id = #head_id) AND (equipment_id = #equipment_id) AND (equipment_attrib_value_deleted = 0)">
<SelectParameters>
<asp:QueryStringParameter Name="equipment_id" QueryStringField="id" Type="Int32" />
<asp:ControlParameter ControlID="heading_id" Name="head_id" PropertyName="Value" Type="Int32" />
</SelectParameters>
</asp:SqlDataSource>
<asp:ListView ID="ListViewAttribValues" runat="server"
DataSourceID="SqlDataSourceAttribValues">
<EmptyDataTemplate>
<table id="Table2" runat="server" style="">
<tr><td>No data was returned.</td></tr>
</table>
</EmptyDataTemplate>
<ItemTemplate>
<tr style="">
<td><asp:Label ID="equipment_attrib_value_detailsLabel" runat="server" Text='<%# Eval("equipment_attrib_value_details") %>' /></td>
</tr>
</ItemTemplate>
<LayoutTemplate>
<table ID="itemPlaceholderContainer" runat="server" border="0" style="">
<tr ID="itemPlaceholder" runat="server">
</tr>
</table>
</LayoutTemplate>
</asp:ListView>
</ItemTemplate>
</asp:TemplateField>

Answer 2

This only works (it seems) if the HiddenField is inside the same ItemTemplate. If the DataSource is somewhere outside the TemplateField, in cases where you want to data-populate a control that is say on another column or field of the GridView, then the HiddenField will not work, as it's technically hidden.
The way to overcome this is in code-behind. Here is how I do it...
I have a TemplateField that is referring to #StudentID, which is actually a HiddenField in another TemplateField.
<asp:TemplateField HeaderText="Currently<br/>Tracking<br/>(past weeks)">
<ItemTemplate>
<asp:CheckBoxList ID="listWeeksTracking" runat="server" DataSourceID="sdsTETpastWeeks" DataTextField="WeekNo" DataValueField="WeekNo"
OnDataBound="listWeeksTracking_DataBound" OnDataBinding="listWeeksTracking_DataBinding"></asp:CheckBoxList>
<br />
<asp:SqlDataSource ID="sdsTETpastWeeks" runat="server" ConnectionString="<%$ ConnectionStrings:ATCNTV1ConnectionString %>"
SelectCommand="SELECT tb.WeekNo, ISNULL((SELECT TOP 1 ts.ETRTWtracking FROM tblTETMeetingStudent AS ts INNER JOIN tblTETMeeting AS tm ON tm.TETmeetingID = ts.TETmeetingID AND tm.WeekNo = tb.WeekNo WHERE ts.StudentID = #StudentID),0) AS Tracking FROM tblTETInstructionalTrainingBlocks AS tb WHERE tb.WeekNo <= #WeekNo AND tb.Active = 1 AND tb.YearNum = YEAR(#TETdate) ORDER BY tb.WeekNo">
<SelectParameters>
<asp:Parameter Name="StudentID" Type="string" />
<asp:ControlParameter ControlID="ddlWeekNo" Name="WeekNo" PropertyName="SelectedValue" Type="int16" />
<asp:ControlParameter ControlID="lblTETdate" Name="TETdate" Type="DateTime" />
</SelectParameters>
</asp:SqlDataSource>
</ItemTemplate>
<ItemStyle HorizontalAlign="Center" />
<HeaderStyle Wrap="False" />
</asp:TemplateField>
So I define the #StudentID parameter as simple a parameter, and not a ControlParameter, is it won't be able to pick up the hiddenfield elsewhere in my GridView.
In code-behind (C#), I trap the Selecting event via the DataBinding.
And in there I specifically look for the row in relation to the control I've just populated (or about to), and then I look for the HiddenField.
protected void listWeeksTracking_DataBinding(object sender, EventArgs e)
{
//set the parameter for the StudentID here as using hiddenfields does not work directly in asp.net, as they are hidden!
CheckBoxList cbl1 = (CheckBoxList)sender;
GridViewRow gvRow = (GridViewRow)cbl1.NamingContainer;
if (gvRow != null)
{
SqlDataSource sdsTETpastWeeks = (SqlDataSource)gvRow.FindControl("sdsTETpastWeeks");
HiddenField hfStudentID = (HiddenField)gvRow.FindControl("hfStudentID");
if (hfStudentID != null) sdsTETpastWeeks.SelectParameters["StudentID"].DefaultValue = hfStudentID.Value.ToString();
}
}
Voila!