Impersonating a Windows user

try this :

[DllImport("advapi32.dll", SetLastError = true)]
    public static extern bool LogonUser(
            string lpszUsername,
            string lpszDomain,
            string lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            out IntPtr phToken);

Usage :

IntPtr userToken = IntPtr.Zero;

bool success = External.LogonUser(
  "john.doe", 
  "domain.com", 
  "MyPassword", 
  (int) AdvApi32Utility.LogonType.LOGON32_LOGON_INTERACTIVE, //2
  (int) AdvApi32Utility.LogonProvider.LOGON32_PROVIDER_DEFAULT, //0
  out userToken);

if (!success)
{
  throw new SecurityException("Logon user failed");
}

using (WindowsIdentity.Impersonate(userToken))
{
 Process.Start("explorer.exe", @"/root,\\server01-Prod\abc");
}

If I'm understanding correctly, your intention is to run the process in the impersonation context.

The doc from CreateProcess (which is used by Process.Start) says: If the calling process is impersonating another user, the new process uses the token for the calling process, not the impersonation token. To run the new process in the security context of the user represented by the impersonation token, use the CreateProcessAsUser or CreateProcessWithLogonW function.

So, you're using the wrong API for doing that.

Instead of using your Impersonator class, what happens when you call Process.Start and pass in a ProcessStartInfo instance that contains the username, password and domain that you want to run the process as?

Perhaps, if that works, then your Impersonator class should create a ProcessStartInfo instance and use that to create new processes (encapsulate that within the class itself).

var psi = new ProcessStartInfo("explorer.exe", @"/root,\\server01-Prod\abc");
psi.Domain = domain;
psi.UserName = username;
psi.Password = password;
psi.WorkingDirectory = workingDir;

Process.Start(psi);

Also, per the MSDN docs...

Setting the Domain, UserName, and the Password properties in a ProcessStartInfo object is the recommended practice for starting a process with user credentials.

You should also set the working directory when starting a process with different user creds.