static void MapOne() { List <string> l = new List <string>( new string[] { "Stefany", "Oussama", "Sebastien", "Frederik" }); Converter <string, bool> pred = delegate(string s) { return(s.StartsWith("S")); }; FastFunc <string, bool> ff = FuncConvert.ToFastFunc <string, bool>(pred); IEnumerable <string> ie = DemoModule.filterStringList(ff, l); foreach (string s in ie) { Console.WriteLine(s); } }