Restarting (Recycling) an Application Pool

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.

Below method is tested to be working for both IIS7 and IIS8

Step 1 : Add reference to Microsoft.Web.Administration.dll. The file can be found in the path C:\Windows\System32\inetsrv\, or install it as NuGet Package https://www.nuget.org/packages/Microsoft.Web.Administration/

Step 2 : Add the below code

using Microsoft.Web.Administration;

Using Null-Conditional Operator

new ServerManager().ApplicationPools["Your_App_Pool_Name"]?.Recycle();

OR

Using if condition to check for null

var yourAppPool=new ServerManager().ApplicationPools["Your_App_Pool_Name"];
if(yourAppPool!=null)
    yourAppPool.Recycle();

Recycle code working on IIS6:

    /// <summary>
    /// Get a list of available Application Pools
    /// </summary>
    /// <returns></returns>
    public static List<string> HentAppPools() {

        List<string> list = new List<string>();
        DirectoryEntry W3SVC = new DirectoryEntry("IIS://LocalHost/w3svc", "", "");

        foreach (DirectoryEntry Site in W3SVC.Children) {
            if (Site.Name == "AppPools") {
                foreach (DirectoryEntry child in Site.Children) {
                    list.Add(child.Name);
                }
            }
        }
        return list;
    }

    /// <summary>
    /// Recycle an application pool
    /// </summary>
    /// <param name="IIsApplicationPool"></param>
    public static void RecycleAppPool(string IIsApplicationPool) {
        ManagementScope scope = new ManagementScope(@"\\localhost\root\MicrosoftIISv2");
        scope.Connect();
        ManagementObject appPool = new ManagementObject(scope, new ManagementPath("IIsApplicationPool.Name='W3SVC/AppPools/" + IIsApplicationPool + "'"), null);

        appPool.InvokeMethod("Recycle", null, null);
    }

Another option:

System.Web.Hosting.HostingEnvironment.InitiateShutdown();

Seems better than UploadAppDomain which "terminates" the app while the former waits for stuff to finish its work.

Here is a simple solution if you just want to recycle all the app pools on the current machine. I had to "run as administrator" for this to work.

using (var serverManager = new ServerManager())
{
    foreach (var appPool in serverManager.ApplicationPools)
    {
        appPool.Recycle();
    }
}