Check if this filter should allow the event to be logged
see remarks
The rendered message is matched against the StringToMatch. If the StringToMatch occurs as a substring within the message then a match will have occurred. If no match occurs this function will return Neutral allowing other filters to check the event. If a match occurs then the value of AcceptOnMatch is checked. If it is true then Accept is returned otherwise Deny is returned.
StringMatchFilter Class | log4net.Filter Namespace