Delay AppDomain recycle on folder change

Question

I am developing a ASP.NET 4 app and use full IIS also during development (for several reasons; one that I use multiple domains pointing to the app). When I build the project in Visual Studio IIS does recycle the AppDomain and loads the newly built one, but now I have the problem, that it does this "to fast". I have some scripts on my page which trigger an App-Startup as soon as it is recycled (like constantly open SignalR channels) and so a new AppDomain is already created when only half of my project is built and so it recycles a second time which then actually crashes, because I have a `PreApplicationStartMethod` copying some Plugin-DLL's to a Shadow-Copy directory, but the "old DLL's" are still locked by the first AppDomain. If I then wait ~10s everything is fine and my "new AppDomain" starts up. I though of solving this problem by simply telling IIS to wait with the rececly for a few seconds so the build can complete after it detects the changes in the `bin` folder. So to my main…

Accepted Answer

If you can't delay the AppDomain recycle, you may want to disable it.

There is a File Change Notification (FCN) behavior which can be disabled.

Registry

Originally, it is a DWORD registry entry at `HKLM\Software\Microsoft\ASP.NET\FCNMode`, setting the value to 1 should disable it.

Code (hack) up to .NET Framework 4.0

This hack might work with 2.0-3.5 and 4.0 frameworks.

```
//Disable AppDomain restart on file change

System.Reflection.PropertyInfo p = 
    typeof(System.Web.HttpRuntime).GetProperty("FileChangesMonitor", 
        System.Reflection.BindingFlags.NonPublic 
        | System.Reflection.BindingFlags.Public 
        | System.Reflection.BindingFlags.Static);

object fcm = p.GetValue(null, null);

System.Reflection.MethodInfo m = fcm.GetType().GetMethod("Stop",
    System.Reflection.BindingFlags.Instance 
    | System.Reflection.BindingFlags.NonPublic); 
m.Invoke(fcm, new object[] { }); 
```

Drop it in your `Global.asax` `Application_Start`. See here.

If you want to disable the monitoring for specific paths or files you can use `StopMonitoringFile` or `StopMonitoringPath` methods from `FileChangesMonitor`. However, `Bin` directory is a special dir and may be immune to these two methods.

At least, you can play with the `_dirMonSpecialDirs` field and call `StopMonitoring()` on your `Bin` directory.

.NET Framework 4.5

In .NET Framework 4.5, a HttpRuntimeSection.FcnMode property exists. There is not so much documentation about it but you can use `<httpRuntime fcnMode="Disabled"/>`.

Delay AppDomain recycle on folder change

Solution

Problem