public abstract class FilterSkeleton : IFilter, 
	IOptionHandler

Public MustInherit Class FilterSkeleton
	Implements IFilter, IOptionHandler

public ref class FilterSkeleton abstract : IFilter, 
	IOptionHandler

[<AbstractClassAttribute>]
type FilterSkeleton =  
    class
        interface IFilter
        interface IOptionHandler
    end

The FilterSkeleton type exposes the following members.

	Name	Description
	FilterSkeleton	Initializes a new instance of the FilterSkeleton class

	Name	Description
	Next	Property to get and set the next filter

	Name	Description
	ActivateOptions	Initialize the filter with the options set
	Decide	Decide if the LoggingEvent should be logged through an appender.
	Equals	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an Object to attempt to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a String that represents the current Object. (Inherited from Object.)

Users should extend this class to implement customized logging event filtering. Note that Logger and AppenderSkeleton, the parent class of all standard appenders, have built-in filtering rules. It is suggested that you first use and understand the built-in rules before rushing to write your own custom filters.

This abstract class assumes and also imposes that filters be organized in a linear chain. The Decide(LoggingEvent) method of each filter is called sequentially, in the order of their addition to the chain.

The Decide(LoggingEvent) method must return one of the integer constants Deny, Neutral or Accept.

If the value Deny is returned, then the log event is dropped immediately without consulting with the remaining filters.

If the value Neutral is returned, then the next filter in the chain is consulted. If there are no more filters in the chain, then the log event is logged. Thus, in the presence of no filters, the default behavior is to log all logging events.

If the value Accept is returned, then the log event is logged without consulting the remaining filters.

The philosophy of log4net filters is largely inspired from the Linux ipchains.

Reference