There's a ControlTemplate named "AutoCompleteStringFilterEditorTemplate" in the GridView which looks like this:
<ControlTemplate x:Key="AutoCompleteStringFilterEditorTemplate" TargetType="grid:AutoCompleteStringFilterEditor"> <Grid MinWidth="100"> <Grid.ColumnDefinitions>I wonder if the MinWidth should really be there? It will effect the width of the column when sizing to headersize, and when setting the column MinWidth manually values < 100 will not work. Columns with other types of filter-editors works better.