System.Collections.Specialized.StringDictionary sdEnvVars = new System.Collections.Specialized.StringDictionary();
System.Diagnostics.ProcessStartInfo psi = new System.Diagnostics.ProcessStartInfo();
sdEnvVars = psi.EnvironmentVariables;
foreach (System.Collections.DictionaryEntry de in sdEnvVars)
{
    Console.WriteLine(de.Key.ToString() + " - " + de.Value.ToString());
}