AvalonEditor SearchPanel

AvalonEditor SearchPanel

I use avalonEdit:TextEditor to show XML-Files and want to add the
Search-Function using ICSharpCode.AvalonEdit.Search.SearchPanel:
SearchPanel sp = new SearchPanel();
sp.Attach(textEditor.TextArea);
sp.Open();
It works well, but the text box in the panel does not have focus. The
method "Reactivate" doesn't work either. Can anyone tell me how to set the
focus on the text box in SearchPanel? Thank you!