The TempFileCollection.Delete method examines each file in the collection to determine, on an individual basis, whether the file is to be kept or deleted. Files can be explicitly marked to be kept when added to the collection using add methods that take a keepFile parameter. When adding a file to the collection using the TempFileCollection.AddExtension(string) overload that does not have a keepFile parameter the value of the TempFileCollection.KeepFiles property is used as the default keep file indicator.