System.Environment.GetEnvironmentVariableCore C# (CSharp) Method

        private static string GetEnvironmentVariableCore(string variable, EnvironmentVariableTarget target)
        {
            if (target == EnvironmentVariableTarget.Process)
            {
                return GetEnvironmentVariableCore(variable);
            }
            else
            {
                RegistryKey baseKey;
                string keyName;

                if (target == EnvironmentVariableTarget.Machine)
                {
                    baseKey = Registry.LocalMachine;
                    keyName = @"System\CurrentControlSet\Control\Session Manager\Environment";
                }
                else
                {
                    Debug.Assert(target == EnvironmentVariableTarget.User);
                    baseKey = Registry.CurrentUser;
                    keyName = "Environment";
                }

                using (RegistryKey environmentKey = baseKey.OpenSubKey(keyName, writable: false))
                {
                    return environmentKey?.GetValue(variable) as string;
                }
            }
        }