Okay.  I figured it out (with help). 

Apparently, it had nothing to do with the 'selectWhere' function.  The problem was in the function: igcmbo_getComboById.  When I simply put in the ID of my webcombo, it was coming back with Null.  I had to put in:

 '<%=WebCombo1.ClientID %>'

as the argument to the function.  Now it's properly filtering the webcombo.

 Thanks again for your assistance.

Hi.  Thank you again for your response.

 I wired up the InitializeDataSource and it seems to be working, however, it seems that the selectWhere function will only work with certain datasources:

"The method will work only with DataSources that support SQL statements (SqlDbAdapter, SqlDataSourceControl for CLR2 etc.). "

 Is there a way to make an AJAX call to filter a datatable if that is the datasource of the WebCombo?

Thanks.

Yes, at one point we were uncertain about InitializeDataSource and even though we kept it for backwards compatibility it was not availble in the property grid events page. Then we got it back. In any way, it is still working you just need to hook it with code in the OnInit event of the page

Example:

    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);
        WebCombo1.InitializeDataSource += new Infragistics.WebUI.WebCombo.InitializeDataSourceEventHandler(WebCombo1_InitializeDataSource);
    }

    void WebCombo1_InitializeDataSource(object sender, Infragistics.WebUI.WebCombo.WebComboEventArgs e)
    {
        // bind here 
    }

Hi.  Thank you again for your response.

 I'm using version 8.1.  InitializeDataSource on the Grid works fine, but not on the WebCombo.  The sample is using an AccessDataSource where I'm trying to assign the Datasource using a datatable in the code behind.  I'm guessing that you don't need an InitializeDataSource when you have a DataSourceID set.  I have the javascript working up until the selectWhere function, but since I can't set EnableXmlHTTP="True" without an InitializeDataSource, and since InitializeDataSource doesn't seem to be an option with my WebCombo, I can't get the dropdown filter to work.

I would appreciate any more suggestions.

Hello,

Looking at the source code for the sample, I do not see InitializeDataSource used there for combobox - did you start from the source code posted there (in the code tabs above the example). Also, if I am not mistaken, InitializeDataSource at one point was removed from grid and then re-added again - could this be a version thing? Which version are you using?