Hello,

Thank you for the question.

After I investigate this filter issue, it seems the issue occurs due to we want to filter the column when the column hasn’t rendered yet.

I attached 2 WebGrid samples which show that we should / can filter a column after the column is already rendered (ready to be filtered)

In this sample, I bind the WebGrid programmatically (with OleDbConnection).
I add filtering code in PrepareDataBinding server side event. In that event I also add RetrieveStructure() method (to retrieve Column's structure).

In the first WebGrid sample, I put the RetrieveStructure() method “before” filtering code. The result is the filtering works fine.
Here’s the snippet code:

protected void WebGrid1_PrepareDataBinding(object sender, ISNet.WebUI.WebGrid.DataSourceEventArgs e){
    if (!IsPostBack)
    {
        WebGrid1.RetrieveStructure();
        WebGridFilter fltr = new WebGridFilter("ShipName", ColumnFilterType.Contain, "Vins");
        WebGrid1.RootTable.FilteredColumns.Add(fltr);            
    }
}

In the second sample, I put the RetrieveStructure() method “after” filtering code. The result is I got the same error message as yours.
Here’s the snippet code:

protected void WebGrid1_PrepareDataBinding(object sender, ISNet.WebUI.WebGrid.DataSourceEventArgs e)
{
    if (!IsPostBack)
    {
        WebGridFilter fltr = new WebGridFilter("ShipName", ColumnFilterType.Contain, "Vins");
        WebGrid1.RootTable.FilteredColumns.Add(fltr);
        WebGrid1.RetrieveStructure();
    }
}

Therefore, please kindly re-check / review your application’s code, whether the column is already rendered or not, when you try to filter it.

Hope this helps.

Regards,
Hans.