What are you using to try to access the node in this XPath? Is this XSL or .NET? Is the bac namespace actually defined (i.e. xmlns:bac="something")?

i use XMLSPY to evaluate the xpath query before i use it in my code. i use
VB.net w/Visual Studio.net 2005. if i add a nameperfix in the InstanceNumber
node bac:InstanceNumber then this query will work

/Site/Networks/Network/bac:BACnetDevices/bac:BACnetDevice/@bac:InstanceNumber

how do i get the value of InstanceNumber without adding "bac:" to the
InstanceNumber node on the xml file.

here is the xml file that i'm working with

<Site InstanceNumber="7415">
    <ActionGroups/>
    <Bookmarks AllowCreate="1" AllowDelete="1">
        <Bookmark Name="HomePage" Path="800.7415_316.11_311.1094"/>
    </Bookmarks>
    <EquipmentCatalogs AllowCreate="0" AllowDelete="1" AllowRename="0">
        <EquipmentCatalog InstanceNumber="133">
            <GeneralProperties Attr="1" InstanceNumber="133" IsConfigured="0"
ObjectName="H280_Strake_Jesuit" ObjectType="317" SchemaVer="1.4"
TraceOptions="0">
                <Description/>
            </GeneralProperties>
        </EquipmentCatalog>
    </EquipmentCatalogs>
    <GeneralProperties Attr="1" InstanceNumber="7415" IsConfigured="0"
ObjectName="H280_Strake_Jesuit" ObjectType="800" SchemaVer="1.4"
TraceOptions="0">
        <Description><![CDATA[eBuilding Main Site]]></Description>
    </GeneralProperties>
    <Networks>
        <Network InstanceNumber="101">
            <bac:BACnetDevices xmlns:bac="http://www.teletrol.com/BACnet">
                <bac:BACnetDevice APDUTimeout="" ApplicationSoftwareVersion=""
FirmwareRevision="" InstanceNumber="3744" MaxAPDULengthAccepted=""
ModelName="" NumberOfAPDURetries="" ProtocolConformanceClass=""
ProtocolObjectTypesSupported="" ProtocolServicesSupported=""
ProtocolVersion="" SegmentationSupported="" VendorIdentifier="" VendorName="">
                    <GeneralProperties Attr="1" InstanceNumber="3744" IsConfigured="0"
ObjectName="Building_1" ObjectType="8" SchemaVer="1.4" TraceOptions="0">
                        <Description/>
                    </GeneralProperties>
                </bac:BACnetDevice>
            </bac:BACnetDevices>
            <GeneralProperties Attr="0" InstanceNumber="101" IsConfigured="0"
ObjectName="Network" ObjectType="801" SchemaVer="1.4" TraceOptions="">
                <Description/>
            </GeneralProperties>
            <NetworkControllers>
                <NetworkController InstanceNumber="115" InternalType="10">
                    <GeneralProperties Attr="1" InstanceNumber="115" IsConfigured="1"
ObjectName="H280_Strake_Jesuit_Plant" ObjectType="8" SchemaVer="1.4"
TraceOptions="0">
                        <Description><![CDATA[Teletrol Systems, Inc. eBuilding Network
Controller model 110]]></Description>
                    </GeneralProperties>
                </NetworkController>
                <NetworkController InstanceNumber="116" InternalType="10">
                    <GeneralProperties Attr="1" InstanceNumber="116" IsConfigured="1"
ObjectName="H280_Strake_Jesuit_Ahu" ObjectType="8" SchemaVer="1.4"
TraceOptions="0">
                        <Description><![CDATA[Teletrol Systems, Inc. eBuilding Network
Controller model 110]]></Description>
                    </GeneralProperties>
                </NetworkController>
                <NetworkController InstanceNumber="1264" InternalType="10">
                    <GeneralProperties Attr="1" InstanceNumber="1264" IsConfigured="0"
ObjectName="H280_Strake_Jesuit_FH" ObjectType="8" SchemaVer="1.4"
TraceOptions="0">
                        <Description><![CDATA[Teletrol Systems, Inc. eBuilding Network
Controller model 120. (Field House controller)
]]></Description>
                    </GeneralProperties>
                </NetworkController>
                <NetworkController InstanceNumber="3764" InternalType="10">
                    <GeneralProperties Attr="1" InstanceNumber="3764" IsConfigured="0"
ObjectName="eNC_Model_130" ObjectType="8" SchemaVer="1.4" TraceOptions="0">
                        <Description><![CDATA[Teletrol Systems, Inc. eBuilding Network
Controller model 130]]></Description>
                    </GeneralProperties>
                </NetworkController>
            </NetworkControllers>
            <NetworkProperties NetworkNumber="1" ProtocolName="">
                <Description/>
                <PropertiesEx/>
            </NetworkProperties>
        </Network>
    </Networks>
    <Queries/>
    <SharedObjects/>
    <SiteProperties IpAddress="" NextInstanceNumber="3771" SiteServerVersion=""/>
    <Facility FacilityIndexURL="" IndexPageURL="" InstanceNumber="11"
minimizedMenu="0" showAlarmIcon="1" showMenu="1" showSaveIcon="1">
        <GeneralProperties Attr="1" InstanceNumber="11" IsConfigured="0"
ObjectName="Facility" ObjectType="316" SchemaVer="1.4" TraceOptions="">
            <Description><![CDATA[Set of Facility Pages]]></Description>
        </GeneralProperties>
    </Facility>
    <Globals InstanceNumber="3">
        <GeneralProperties Attr="1" InstanceNumber="3" IsConfigured="0"
ObjectName="Globals" ObjectType="201" SchemaVer="1.4" TraceOptions="0">
            <Description><![CDATA[Location for all Global System
Objects]]></Description>
        </GeneralProperties>
    </Globals>
</Site>

i got it. by using namespace manager the xpath query work in my VB.net code.