Programatically uninstall Windows Service from .NET

Question

After searching the web for information, I have managed to create a service which, depending on the command line, can install or uninstall itself, or just run as an application.

However, the uninstalling code isn't working correctly.

The related code:

Private Function UnInstallService(ByVal args As String(), ByRef errMsg As String) As Boolean
    Dim si As New ServiceInfo

    If (Not GetServiceInfo(args, si)) Then
        errMsg = "Error..."
        Return False
    End If

    If (Not IsServiceInstalled(si.Name)) Then
        errMsg = "Error..."
        Return False
    End If

    Try
        Dim installer As ServiceProcessInstaller = GetServiceInstaller(si)
        Dim stateSaver As IDictionary = New Hashtable
        Try
            installer.Uninstall(stateSaver)
        Catch e As exception
            errMsg = "Error..."
            Return False
        End Try
    Catch e As exception
        errMsg = "Error..."
        Return False
    End Try
End Function

Private Function GetServiceInstaller(ByVal si As ServiceInfo) As ServiceProcessInstaller
    Dim installer As ServiceInstaller = New ServiceInstaller()
    Dim pInstaller As New ServiceProcessInstaller
    pInstaller.Context = New InstallContext("", si.CommandLine)

    installer.Description = si.Description
    installer.DisplayName = si.DisplayName
    installer.ServiceName = si.Name
    installer.StartType = ServiceStartMode.Automatic

    If (si.Account = "LocalSystem") Then
        pInstaller.Account = ServiceAccount.LocalSystem
    ElseIf (si.Account = "LocalService") Then
        pInstaller.Account = ServiceAccount.LocalService
    ElseIf (si.Account = "NetworkService") Then
        pInstaller.Account = ServiceAccount.NetworkService
    Else
        pInstaller.Account = ServiceAccount.User
        pInstaller.Password = si.Password
        pInstaller.Username = si.Account
    End If

    pInstaller.Context.Parameters("assemblypath") = si.FullPath

    pInstaller.Installers.Add(installer)
    installer.Parent = pInstaller

    Return pInstaller
End Function

It throws a NullReferenceException in the call to installer.Uninstall The code for installation is exactly the same, except for checking if the service is installed, and calling installer.Install and then installer.Commit instead of Uninstall. I'm passing it exactly the same parameters.

Any idea?

Answer 1

Your code seems a bit longwinded, all I do to uninstall is call:

 Dim path As String = Assembly.GetExecutingAssembly().Location
 ManagedInstallerClass.InstallHelper(New String() {"/u", path})

To install all I do is:

 Dim path As String = Assembly.GetExecutingAssembly().Location
 ManagedInstallerClass.InstallHelper(New String() {path})

And then I've got some code in the constructor of my ProjectInstaller that sets username etc

Edit: Though be aware that the documentation for the ManagedInstallerClass has the following quote: This API supports the .NET Framework infrastructure and is not intended to be used directly from your code.
So it might not be future proof to use it from your own code...

Answer 2

I have found the problem here: http://social.msdn.microsoft.com/Forums/en-US/netfxbcl/thread/58505d7b-cb78-4486-88fc-9b86890664e0

The problem lies in the line

installer.Uninstall(stateSaver)

which, instead, should have been

installer.Uninstall(Nothing)