Finding App Pool Memory Usage

I need to figure out an way to display the memory used by each application pool in the current machine - IIS in C# code. I am able to figure out the state of an app pool using the following code.

                string appPoolPath = @"IIS://" + currentserverName + "/W3SVC/AppPools/" + appPoolName;

                int intStatus = 0;

                try
                {

                    DirectoryEntry w3svc = new DirectoryEntry(appPoolPath);
                    intStatus = (int)w3svc.InvokeGet("AppPoolState");
                    switch (intStatus)
                    {
                        case 2:
                            status = "Running";
                            break;
                        case 4:
                            status = "Stopped";
                            break;
                        default:
                            status = "Unknown-" + intStatus.ToString();
                            break;
                    }
                }
                catch (Exception ex)
                {
                    throw ex;
                }

But I also need the CPU Usage so that this can be a tool to assess the status of the applications pools.