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vb.net and wmi (win32_printer)

Posted on 2014-11-10
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Last Modified: 2014-11-10
I am running the below code to call remote workstation printers that are installed.  This works for my local machine but fails on remote machine.  It errors out with "object reference not set to an instance of this object".  Weird part is i call similar code for remote running processes and it works fine:

Printer Code:

 Dim RC As String = TextBox1.Text
        'Try
        Dim theScope As New ManagementScope("\\" & RC & "\root\cimv2")
        Dim objectQuery As New ObjectQuery("SELECT * FROM Win32_Printer")
        For Each managementObject As ManagementObject In (New ManagementObjectSearcher(theScope, objectQuery)).[Get]()
            Dim str As String = managementObject("Name").ToString()
            lvprinter.Groups.Add(str, str)

            Dim item As New ListViewItem("Driver")
            item.SubItems.Add(managementObject("DriverName").ToString())
            item.Group = lvprinter.Groups(str)
            lvprinter.Items.Add(item)

            item = New ListViewItem("PortName")
            item.SubItems.Add(managementObject("PortName").ToString())
            item.Group = lvprinter.Groups(str)
            lvprinter.Items.Add(item)

            item = New ListViewItem("Status")
            item.SubItems.Add(managementObject("Status").ToString())
            item.Group = lvprinter.Groups(str)
            lvprinter.Items.Add(item)
        Next

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Code for calling remote processes that work fine:

 Dim RC As String = TextBox1.Text
        Try
            ListView2.Items.Clear()

            Dim theScope As New ManagementScope("\\" & RC & "\root\cimv2")
            Dim objectQuery As New ObjectQuery("SELECT * FROM Win32_Process")
            ListView2.Groups.Add(New ListViewGroup("Processes", "Process List"))
            For Each managementObject As ManagementObject In (New ManagementObjectSearcher(theScope, objectQuery)).[Get]()
                Dim item As ListViewItem = ListView2.Items.Add(managementObject("Name").ToString())
                item.SubItems.Add(managementObject("ProcessId").ToString())
                item.Group = ListView2.Groups("Processes")
            Next
        Catch ex As Exception
        End Try

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Question by:derek7467
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Accepted Solution

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derek7467 earned 0 total points
ID: 40433015
Figured it out, status isnt always a result so i had to wrap in a try-catch

try
query printers
Catch exception As Exception
End Try
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