Public ReadOnly Property PID As Integer

public int PID {get;}

using (ProcessRunner runner = new ProcessRunner("cmd.exe"))
{
    StringWriter wtr = new StringWriter();
    StringWriter err = new StringWriter();
    ProcessOutputEventHandler handler =
            delegate(object o, ProcessOutputEventArgs e)
            { if (e.Error) err.WriteLine(e.Data); else wtr.WriteLine(e.Data); };

    runner.OutputReceived += handler;

    Assert.AreEqual(0, runner.Run("/C", "dir", "/b", "/on", "/ad-h-s", "c:\\"));
    Assert.AreEqual(String.Empty, err.ToString());

    Assert.AreNotEqual(0, runner.PID);

    StringReader rdr = new StringReader(wtr.ToString());
    List<DirectoryInfo> rootdirs = new List<DirectoryInfo>(new DirectoryInfo("C:\\").GetDirectories());
    rootdirs.Sort(delegate(DirectoryInfo x, DirectoryInfo y) { return StringComparer.OrdinalIgnoreCase.Compare(x.Name, y.Name); });
    foreach (DirectoryInfo di in rootdirs)
    {
        if ((di.Attributes & (FileAttributes.Hidden | FileAttributes.System)) != 0)
            continue;
        Assert.AreEqual(di.Name, rdr.ReadLine());
    }

    Assert.AreEqual(null, rdr.ReadLine());
}

Using runner As New ProcessRunner("cmd.exe")
    Dim wtr As New StringWriter()
    Dim err As New StringWriter()
    Dim handler As ProcessOutputEventHandler = Function(o As Object, e As ProcessOutputEventArgs) Do
        If e.[Error] Then
            err.WriteLine(e.Data)
        Else
            wtr.WriteLine(e.Data)
        End If
    End Function

    runner.OutputReceived += handler

    Assert.AreEqual(0, runner.Run("/C", "dir", "/b", "/on", "/ad-h-s", "c:\"))
    Assert.AreEqual([String].Empty, err.ToString())

    Assert.AreNotEqual(0, runner.PID)

    Dim rdr As New StringReader(wtr.ToString())
    Dim rootdirs As New List(Of DirectoryInfo)(New DirectoryInfo("C:\").GetDirectories())
    rootdirs.Sort(Function(x As DirectoryInfo, y As DirectoryInfo) Do
        Return StringComparer.OrdinalIgnoreCase.Compare(x.Name, y.Name)
    End Function)
    For Each di As DirectoryInfo In rootdirs
        If (di.Attributes And (FileAttributes.Hidden Or FileAttributes.System)) <> 0 Then
            Continue For
        End If
        Assert.AreEqual(di.Name, rdr.ReadLine())
    Next

    Assert.AreEqual(Nothing, rdr.ReadLine())
End Using