FX7400 and filtering.

I have gone through the VB_RFID3_Host_Sample2 application that comes with the EMDK and was trying to figure out the filtering and am having some trouble setting filters and I guess fully understanding them.  I went through the help content and found a section on coding pre and post filters, along with RSSI filters.  I was able(I think) to get the RSSI filters to work, but I am having some trouble with the pre and post.  Below is the VB.net code I have added to the sample, that if I am understanding the help sample correctly, should not read tags starting with the character 6(hex 36). i have tags that have different id's and when i run this, it finds no tags, but when i clear the filter and try again, it reads all the tags.     Basically what i did in the sample app was added another button that ran this code(along with another button to clear the filters), and then i just clicked the start reading and I expect tags without a start value of six to be read, but they are not.

Can someone assist me in figuring out the issue?




                    Dim filter As New PreFilters.PreFilter()

                    Dim tagMask As Byte() = New Byte(0) {&H36}

                    filter.AntennaID = 1

                    filter.TagPattern = tagMask

                    filter.TagPatternBitCount = CUInt(tagMask.Length) * 8

                    filter.BitOffset = 32

                    filter.MemoryBank = MEMORY_BANK.MEMORY_BANK_TID

                    filter.FilterAction = FILTER_ACTION.FILTER_ACTION_STATE_UNAWARE

                    filter.StateUnawareAction.Action = STATE_UNAWARE_ACTION.STATE_UNAWARE_ACTION_UNSELECT

                    ' do not select the tags that match the pre-filter criteria