ReplaceBetweenTags function with delegate to describe transformation

I've created a function that allow to replace content between XML tags with data, that depend on original content within tag, in particular to MAsk credit card number.

The function uses MidBetween extension from My StringHelper class

 /// <summary>
///
/// </summary>
/// <param name="thisString"></param>
/// <param name="openTag"></param>
/// <param name="closeTag"></param>
/// <param name="transform"></param>
/// <returns></returns>
/// <example>
/// // mask <AccountNumber>XXXXX4488</AccountNumber>
///requestAsString  = requestAsString.ReplaceBetweenTags("<AccountNumber>", "</AccountNumber>", CreditCard.MaskedCardNumber);
///mask cvv
///requestAsString = requestAsString.ReplaceBetweenTags("<FieldName>CC::VerificationCode</FieldName><FieldValue>", "</FieldValue>", cvv=>"XXX");
/// </example>
public static string ReplaceBetweenTags(this string thisString, string openTag, string closeTag, Func<string, string> transform)
{
//See also http://stackoverflow.com/questions/1359412/c-sharp-remove-text-in-between-delimiters-in-a-string-regex
string sRet = thisString;
string between = thisString.MidBetween(openTag, closeTag, true);
if (!String.IsNullOrEmpty(between))
sRet=thisString.Replace(openTag + between + closeTag, openTag + transform(between) + closeTag);
return sRet;
}
public static string ReplaceBetweenTags(this string thisString, string openTag, string closeTag, string newValue)
{
//See also http://stackoverflow.com/questions/1359412/c-sharp-remove-text-in-between-delimiters-in-a-string-regex
string sRet = thisString;
string between = thisString.MidBetween(openTag, closeTag, true);
if (!String.IsNullOrEmpty(between))
sRet = thisString.Replace(openTag + between + closeTag, openTag + newValue + closeTag);
return sRet;
}