Question

In VB.NET, I am trying to retrieve what services are running on a TS using the following code:

Imports System.ServiceProcess
...
Dim dictservice As Generic.Dictionary(Of String, Services)

Public Sub GetService()
    Dim localServices As ServiceController() = ServiceController.GetServices()
    For Each service As ServiceController In localServices
        dictservice.Add(service.DisplayName, New Services(service.DisplayName, service.ServiceName, service.Status.ToString))
    Next
End Sub

My services class is as follows:

Class Services
    Private _displayName As String
    Private _serviceName As String
    Private _serviceStatus As String

    Sub New(ByVal DisplayName As String, ByVal ServiceName As Object, ByVal ServiceStatus As String)
        _displayName = DisplayName
        _serviceName = ServiceName
        _serviceStatus = ServiceStatus
    End Sub

    Public Overrides Function ToString() As String
        Return _serviceStatus
    End Function
End Class

When i step through in debug mode it seems to being to populate the dictionary
display name: Application Experience
service name: AElookUpSVC
service status: Running (4)

When it tries to move onto the next item i get the following error:

Null reference exception was unhandled:
Object reference not set to an instance of an object.

I can’t for the life of me work out where it is finding a null reference?

Answer 1

You need to initialize your dictionary with New:

Dim dictservice As New Generic.Dictionary(Of String, Services)

Public Sub GetService()
    Dim localServices As ServiceController() = ServiceController.GetServices()
    For Each service As ServiceController In localServices
        dictservice.Add(service.DisplayName, New Services(service.DisplayName, service.ServiceName, service.Status.ToString))
    Next
End Sub

Right now it’s Nothing, hence the NullReferenceException.