How to: Customize the Search Form
This example demonstrates how to replace the standard Find and Replace dialog with a custom one via the RichEditControl.SearchFormShowing event.
private void richEditControl1_SearchFormShowing(object sender, SearchFormShowingEventArgs e)
{
string curWord = richEditControl1.Document.GetText(richEditControl1.Document.Selection);
MySearchTextForm form = new MySearchTextForm(e.ControllerParameters, curWord);
e.DialogResult = form.ShowDialog();
e.Handled = true;
}