问如何判断IIS应用程序池被回收的原因

EN

//  obtain the shutdown reason
System.Web.ApplicationShutdownReason shutdownReason = System.Web.Hosting.HostingEnvironment.ShutdownReason;
string shutdownDetail = "";

//Evaluate which option caused the error
switch (shutdownReason)
{
    case ApplicationShutdownReason.BinDirChangeOrDirectoryRename:
        shutdownDetail = "A change was made to the bin directory or the directory was renamed";
        break;
    case ApplicationShutdownReason.BrowsersDirChangeOrDirectoryRename:
        shutdownDetail = "A change was made to the App_browsers folder or the files contained in it";
        break;
    case ApplicationShutdownReason.ChangeInGlobalAsax:
        shutdownDetail = "A change was made in the global.asax file";
        break;
    case ApplicationShutdownReason.ChangeInSecurityPolicyFile:
        shutdownDetail = "A change was made in the code access security policy file";
        break;
    case ApplicationShutdownReason.CodeDirChangeOrDirectoryRename:
        shutdownDetail = "A change was made in the App_Code folder or the files contained in it";
        break;
    case ApplicationShutdownReason.ConfigurationChange:
        shutdownDetail = "A change was made to the application level configuration";
        break;
    case ApplicationShutdownReason.HostingEnvironment:
        shutdownDetail = "The hosting environment shut down the application";
        break;
    case ApplicationShutdownReason.HttpRuntimeClose:
        shutdownDetail = "A call to Close() was requested";
        break;
    case ApplicationShutdownReason.IdleTimeout:
        shutdownDetail = "The idle time limit was reached";
        break;
    case ApplicationShutdownReason.InitializationError:
        shutdownDetail = "An error in the initialization of the AppDomain";
        break;
    case ApplicationShutdownReason.MaxRecompilationsReached:
        shutdownDetail = "The maximum number of dynamic recompiles of a resource limit was reached";
        break;
    case ApplicationShutdownReason.PhysicalApplicationPathChanged:
        shutdownDetail = "A change was made to the physical path to the application";
        break;
    case ApplicationShutdownReason.ResourcesDirChangeOrDirectoryRename:
        shutdownDetail = "A change was made to the App_GlobalResources foldr or the files contained within it";
        break;
    case ApplicationShutdownReason.UnloadAppDomainCalled:
        shutdownDetail = "A call to UnloadAppDomain() was completed";
        break;
    default:
        shutdownDetail = "Unknown shutdown reason";
        break;
}