Restarting (Recycling) an Application Pool

Question

Here we go:

HttpRuntime.UnloadAppDomain();

If you're on IIS7 then this will do it if it is stopped. I assume you can adjust for restarting without having to be shown.

// Gets the application pool collection from the server.
[ModuleServiceMethod(PassThrough = true)]
public ArrayList GetApplicationPoolCollection()
{
    // Use an ArrayList to transfer objects to the client.
    ArrayList arrayOfApplicationBags = new ArrayList();

    ServerManager serverManager = new ServerManager();
    ApplicationPoolCollection applicationPoolCollection = serverManager.ApplicationPools;
    foreach (ApplicationPool applicationPool in applicationPoolCollection)
    {
        PropertyBag applicationPoolBag = new PropertyBag();
        applicationPoolBag[ServerManagerDemoGlobals.ApplicationPoolArray] = applicationPool;
        arrayOfApplicationBags.Add(applicationPoolBag);
        // If the applicationPool is stopped, restart it.
        if (applicationPool.State == ObjectState.Stopped)
        {
            applicationPool.Start();
        }

    }

    // CommitChanges to persist the changes to the ApplicationHost.config.
    serverManager.CommitChanges();
    return arrayOfApplicationBags;
}

If you're on IIS6 I'm not so sure, but you could try getting the web.config and editing the modified date or something. Once an edit is made to the web.config then the application will restart.

Maybe this articles will help:

• Recycle current Application Pool programmatically (for IIS 6+)
• Recycling Application Pools using WMI in IIS 6.0
• Recycling IIS 6.0 application pools programmatically
• Programatically recycle an IIS application pool

The code below works on IIS6. Not tested in IIS7.

using System.DirectoryServices;

...

void Recycle(string appPool)
{
    string appPoolPath = "IIS://localhost/W3SVC/AppPools/" + appPool;

    using (DirectoryEntry appPoolEntry = new DirectoryEntry(appPoolPath))
    {
            appPoolEntry.Invoke("Recycle", null);
            appPoolEntry.Close();
    }
}

You can change "Recycle" for "Start" or "Stop" also.

I went a slightly different route with my code to recycle the application pool. A few things to note that are different than what others have provided:

1) I used a using statement to ensure proper disposal of the ServerManager object.

2) I am waiting for the application pool to finish starting before stopping it, so that we don't run into any issues with trying to stop the application. Similarly, I am waiting for the app pool to finish stopping before trying to start it.

3) I am forcing the method to accept an actual server name instead of falling back to the local server, because I figured you should probably know what server you are running this against.

4) I decided to start/stop the application as opposed to recycling it, so that I could make sure that we didn't accidentally start an application pool that was stopped for another reason, and to avoid issues with trying to recycle an already stopped application pool.

public static void RecycleApplicationPool(string serverName, string appPoolName)
{
    if (!string.IsNullOrEmpty(serverName) && !string.IsNullOrEmpty(appPoolName))
    {
        try
        {
            using (ServerManager manager = ServerManager.OpenRemote(serverName))
            {
                ApplicationPool appPool = manager.ApplicationPools.FirstOrDefault(ap => ap.Name == appPoolName);

                //Don't bother trying to recycle if we don't have an app pool
                if (appPool != null)
                {
                    //Get the current state of the app pool
                    bool appPoolRunning = appPool.State == ObjectState.Started || appPool.State == ObjectState.Starting;
                    bool appPoolStopped = appPool.State == ObjectState.Stopped || appPool.State == ObjectState.Stopping;

                    //The app pool is running, so stop it first.
                    if (appPoolRunning)
                    {
                        //Wait for the app to finish before trying to stop
                        while (appPool.State == ObjectState.Starting) { System.Threading.Thread.Sleep(1000); }

                        //Stop the app if it isn't already stopped
                        if (appPool.State != ObjectState.Stopped)
                        {
                            appPool.Stop();
                        }
                        appPoolStopped = true;
                    }

                    //Only try restart the app pool if it was running in the first place, because there may be a reason it was not started.
                    if (appPoolStopped && appPoolRunning)
                    {
                        //Wait for the app to finish before trying to start
                        while (appPool.State == ObjectState.Stopping) { System.Threading.Thread.Sleep(1000); }

                        //Start the app
                        appPool.Start();
                    }
                }
                else
                {
                    throw new Exception(string.Format("An Application Pool does not exist with the name {0}.{1}", serverName, appPoolName));
                }
            }
        }
        catch (Exception ex)
        {
            throw new Exception(string.Format("Unable to restart the application pools for {0}.{1}", serverName, appPoolName), ex.InnerException);
        }
    }
}