problem while replacing _ with &

[dskp]

while formatting the string by using String.Format() with message "john & berry's",
it displays like "john _berry's".

& is replace by _

[code]
String.Format(StringHelper.GetFASMessagingValue("ListAddOptionConfirm"), Masking == null ? valueMember.Replace(@"&",@"\&") : new string(Masking.MaskedText).Replace(@"&",@"\&"), fieldName);
[\code]

please provide the solution