I think that you don't really need to be doing custom ColumnFilterDescriptors. Setting the default filter operator is described in this article
Hiding the match case button is described in this article
. The pictures are of the FilteringControl but the same logic applies for the FilterRow since the editor is one and the same.
So if you follow these two articles, your users will be able to type something and hit enter and the filter will be applied. They don't even need to open the filter operator drop-down.
So all you need to do is the following:
sender, Telerik.Windows.Controls.GridView.FilterOperatorsLoadingEventArgs e)
e.DefaultOperator = FilterOperator.StartsWith;
sender, Telerik.Windows.Controls.GridView.EditorCreatedEventArgs e)
var editor = e.Editor
editor.MatchCaseVisibility = Visibility.Collapsed;
I have attached a sample project that demonstrates this.
I hope this helps.
the Telerik team