RadGrid filtering using a RadComboBox of checkboxes?

[Chris]

I have a radgrid bound to a sqldatasource, I have the columns using a radcombobox. What I want to do is switch some of the columns to use checkboxes like on this example:
http://demos.telerik.com/aspnet-ajax/combobox/examples/functionality/templates/defaultcs.aspx 
The only other thing I've been able to find on this is from this forum from 2009:
http://www.telerik.com/community/forums/aspnet-ajax/grid/radgrid-filtering-using-a-radcombobox-of-checkboxes.aspx 

But first mine is all declared in the aspx file, and second everything else is changing the filter using a js call like:

var tableView = $find("<%# ((GridItem)Container).OwnerTableView.ClientID %>");
tableView.filter("CustomerName", args.get_item().get_value(), "EqualTo");

While that forum post ends with a:
$find("<%= RadAjaxManager1.ClientID %>").ajaxRequest("ContactTitle," + text ); 
That calls a function on the code behind:

private void RadAjaxManager1_AjaxRequest(object  sender, AjaxRequestEventArgs e)

{

if(e.Argumnet.ToString().Split[','][0]=="ContactTitle")

{

//Access the rest of the string and set the filter Expression

}

}

What is the best way to do what I'm trying to do, and if that's the only way to do the checkboxes (using the ajax call) how do I modify the sqldatasource from the ajax call so that it doesn't mess up the rest of the filtering?

Update:
I created a control that inherits from GridTemplateColumn,
In there I do:

RadComboBox rcBox = new RadComboBox();
            rcBox.ID = "DropDownList_" + DataField;
            rcBox.AutoPostBack = true;
            rcBox.DropDownWidth = DropDownWidth;
            rcBox.Width = FilterControlWidth;
            rcBox.CheckBoxes = true;
            rcBox.ItemChecked += rcBox_ItemChecked;
            rcBox.Height = Unit.Pixel(200);

 	    DataTable table = GetDataTable(string.Format("SELECT DISTINCT cast({0} as varchar) as {0} FROM {1} Where 1=1 {2} order by {0} asc", this.DataField, TableName, where));
            rcBox.DataTextField = this.DataField;
            rcBox.DataValueField = this.DataField;
            rcBox.DataSource = table;
            cell.Controls.Add(rcBox);

my rcBox_ItemChecked looks like this:

private void rcBox_ItemChecked(object sender, Telerik.Web.UI.RadComboBoxItemEventArgs e)
        {
            ((GridFilteringItem)(((RadComboBox)sender).Parent.Parent)).FireCommandEvent("Filter", new Pair());
        }

in the:

protected override void SetCurrentFilterValueToControl(TableCell cell)

and:

protected override string GetCurrentFilterValueFromControl(TableCell cell)
How can I access the checkboxs?
And how do I add or filtering best?

[Pavlina]

Hi Chris,

Can you please try to enable the checkboxes mode of RadComboBox by setting the combobox's CheckBoxes property to "True" and see if it works properly.
http://demos.telerik.com/aspnet-ajax/combobox/examples/functionality/checkboxes/defaultcs.aspx

Additionally, to enable Check All functionality you should set EnableCheckAllItemsCheckBox property to true.

Please give this suggestion a try and let me know how it goes.

Regards,
Pavlina
the Telerik team