"Import-Module virtualmachinemanager" always have error in C# code.

static void Main(string[] args)
        {
            InitialSessionState initial = InitialSessionState.CreateDefault();
            initial.ImportPSModule(new string[] { "virtualmachinemanager" });
            Runspace runspace = RunspaceFactory.CreateRunspace(initial);
            runspace.Open();
            PowerShell ps = PowerShell.Create();
            ps.Runspace = runspace;
            ps.Commands.AddCommand("get-vm");
            try
            {
                Collection<PSObject> list = ps.Invoke();
                foreach (var item in list)
                {
                    Console.WriteLine(item.TypeNames);
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.ReadLine();
        }

I want to get vm list by C#,how can I fix this issue?

Besr regards