parsing "*" - Quantifier {x,y} following nothing

fails when I try Regex.Replace() method. how can i fix it?

Replace.Method (String, String, MatchEvaluator, RegexOptions)

I try code

<%# Regex.Replace( (Model.Text ?? "").ToString(), patternText, "<b>" + patternText + "</b>", RegexOptions.IgnoreCase | RegexOptions.Multiline)%>